PART III. BIOLOGY—OF THE WHOLE IN SINGULARS. (continued 8)

3287. The position of the sexual parts at the posterior extremity of the body has been permanently established, with exceedingly few exceptions, as in some aquatic Insects.

That they correspond to the head, or are imperfect cephalic organs, is most distinctly shown in the Insect. They are usually environed by valves, pincers, and filaments, which resemble maxillæ and palpi.

3288. The Ovum-animals multiply by division, by granules or gemmæ, i. e. shoots, the Sexual animals by membranous ova, the Arthritic animals by horny ova. These last, or egg-shells, are hard, and frequently also so strung together or laid by the parent upon each other as to represent the annulate body of some Insect.

3289. In the ova of the Dermatozoa or Tegumental animals the vitellus only appears to exist, being without albumen, which first seems to make its appearance along with the animal systems. As the animal separates into higher and lower substances, so also does the ovum or microzoon. The simplicity of the Tegumental animals has been prophesied or foretold in that of their ova.

The Insecta, as being the third class of their circle, repeat the Acalephæ and Kracken. With the last they bear much resemblance in form and in their motor organs.

3290. Would we arrange the Worms along with the spiral vessels or ducts, the Crabs with the woody rings in the stem, we must term the Tracheal animals foliage or leaves. Their wings are pinnate leaves, and among the Orthoptera many occur which, as well in the form of the body as of the wings, appear as if they had been just liberated from the Papilionaceous tree. The tales or stories, about leaves changing in the torrid zones into Insects, are not without meaning; for poetry is none other than the Ideal of natural history.

Metamorphosis.

3291. We now proceed to retrace our steps. The Insect is a Tegumental animal represented in limbs. There can be therefore present in the Insect no other development than in the Cutaneous animal, which works itself up into the Branchial and Tracheal animal.

The Insect passes through three stages prior to its attaining the adult or perfect condition. It is at first Worm, next Crab, then a perfect, volant animal with limbs, a Fly.

3292. The representative passage of the Insect through the preceding classes in the course of development, constitutes its metamorphosis. Thus the Insect's metamorphosis obtains a meaning and an explanation. Upon the whole, the history of every kind of pregnancy is none other than the passage which takes place through all the animal classes, as I have first represented in my book upon "Generation" (Von der Zeugung, 1805); but in no class of animals are the periods so dissevered or drawn apart as in Insects. It therefore comes to pass that these animals are the equivalent transcripts or copies of a system common to them and the preceding animals.

3293. The Worm is the first condition of the Insect. It is represented, by the larva, which, according to its diversity of size, is called maggot, caterpillar, grub, &c.

3294. The larva is only a Cutaneous and Intestinal animal. It knows of nothing else but eating like the Worm; it has no sexual function, no lust, nor pain; it can scarcely move; in many the feet are wanting, as in the larvæ of Flies, which thus resemble the Entozoa; many have a crop of lateral papillæ, like the caterpillars, which resemble the Nereids.

3295. The change into a nympha, chrysalis, or pupa, commences with the horny induration met with in the Crab, and in the higher organized kinds of Snail. The pupa is the embryonic Crab or its antetype, it is the Snail in its shell.

3296. In the third condition the Insect makes an advance above the branchial condition, and casts aside the Snail's or Crab's shell; and is then the perfect Insect, the Fly.

3297. The metamorphosis is accordingly the embryonic transition of the Insect, after extrusion from the egg, through the three classes of its circle. In the ovum state it only passes through that of the Intestinal and Sexual animals.

3298. This is a retrospective proof that the higher animals also pass in the ovum through the condition of the lower animals, but after birth through the classes which directly precede them.

What holds good of the Insects, does so also of the preceding groups of animals, although in a less degree; the higher class of each circle still passes after birth through one or other of the inferior classes.

Thus, the Acalephæ first appear under the form of Infusoria; next change into Polyps, and then obtain for the first time the form of the perfect Acalephæ. The same phenomenon occurs in the naked snails or Slugs. They have, when freshly hatched from the egg, a small mussel-like shell, which they lose at a later period.

The Echini or Sea-urchins, which I believe ought to be ranged with the Kracken, also pass through a metamorphosis.

Finally, it is well known that the Crabs also are subjected to a metamorphosis. Their first condition must be regarded as that of the Worm.

The law is thus universal. The second and third class of every circle traverse after birth the classes, to whose series they belong.

It would even appear that the classes, also of a lower circle, are subject to similar changes; at least many Entozoa, and thus the first class of the third circle, appear to undergo such a metamorphosis, since they first of all resemble an Infusory animal, next change as pupæ into Molluscs, and are then manifested for the first time as Worms.

3299. The Dermatozoa or Sensitive animals range in the following manner, according to the anatomical systems:

A. Intestinal animals.B. Vascular animals.C. Respiratory animals.

1. Gastric animals.4. Venous animals.7. Reticular animals.

Infusoria.Mussels.Worms.

2. Intestinal animals.5. Arterial animals.8. Branchial animals.

Polyps.Snails.Crustacea.

3. Absorbent animals.6. Cardiac animals.9. Tracheal animals.

Acalephæ.Kracken.Insects.

3300. According to the developments of the feeling-sense they stand thus:

A. Ovum-animals.B. Sexual animals.C. Cutaneous animals.

1. Vitelline animals.4. Ovarial animals.7. Papillary animals.

Infusoria.Mussels.Worms.

2. Albuminose animals.5. Orchitic animals.8. Pedal animals.

Polyps.Snails.Crustacea.

3. Involucral animals.6. Renal animals.9. Alary animals.

Acalephæ.Kracken.Flies.

3301. From these tables the number and kind of relationships or affinities is readily deduced. There is a Relationship of Proximity, as that between Infusoria, Polyps, and Acalephæ.

A Relationship of Repetition, as of Infusoria, Mussels, Worms. There is also a Relationship of Series, which takes its rise from the parallelism of the classes. The two last relationships have been confounded together under the term analogy, which at best is but a word of random definition.

Second Province—Sarcozoa, Cephalozoa.

FOURTH CIRCLE—SARCOSE ANIMALS.

3302. The system of motion and sensation, which broke forth so forcibly in the tegument, now passes over into other forms, into the globular form of bone, the fibrous form of flesh or muscle, and the point-form of the nerves.

3303. The nervous system when liberated from the vegetative organs is, or consists of, the myelon (spinal chord) and the encephalon, i. e. brain.

3304. These animals are therefore Osseous, Muscular, and Encephalic animals, whereupon the senses are proportionately developed, and constitute the basis of the highest animal forms—Sarcozoa. The Dermatozoa are asarcose or fleshless animals.

3305. With the sudden appearance of the animal systems all organs of the head, such as tongue, nose, ears, and eyes, are also developed; no asarcous animal has nostrils. Now these parts, especially the nostrils, as marking the terminal extremity of the vertebral column, make up the head—Cephalozoa, or Cephalic animals.

Class 10. Osteozoa, Glossozoa.

3306. The animals, in which the osseous system for the first time makes its appearance are, the Fishes.

The Fish alone has more bones than any other animal. It has dorsal rays, which are wanting in all others.

3307. The animal systems are for the first time slightly separated from each other. Bone, muscle, and nerve are rather a gelatinous mass, which only bids fair for becoming something higher; on this account the bones are frequently but soft cartilages or tendons, the muscle composed of white fibres like those upon the intestine or vessels, the nerve thick, oleaginous, and soft in texture, while the brain is in its constituent parts hardly comparable with that of the Thricozoa.

3308. The muscles of Fishes are not yet perfect in character, since they are devoid of individualization and red colour, and their fibres run mostly parallel with each other without uniting into tendons. Their muscular body is a muscular wall.

3309. The Fishes, ranking upon the first stage of the Sarcozoa, repeat the same stage of the preceding circle, and thus the Infusoria, Mussels, and Worms; or the stomach, veins, and branchial rete or network; furthermore, the vitellus, ovary, and skin, which systems must in them accordingly predominate.

Pelvis.

3310. In Fishes the pelvic organs, sexual parts, and tail predominate. The tail, as being an appurtenance of the pelvis, is larger and stronger than in other animals. It mostly makes up the largest part of the body, and is, properly speaking, its only motor organ.

3311. The sexual parts have still the form of the intestine, and occupy the greatest part of the abdomen. The ovaria are two sacs, like two Infusoria, in whose parietes granules are developed; even the testes are only two such sacs or seminal vesicles wherein the "milt" is contained. Fishes may be termed anorchitic, or animals devoid of testes.

The ova are small, consisting of spawn or roe without shell, but they separate into albumen and vitellus.

3312. External sexual parts are not present. Everything usually opens into a cloaca, which is thus here a true pharyngeal cavity.

3313. With the perfected formation of the head, the animal, so to speak, undergoes a sudden and entire change, and the sexual parts are developed with all their accessory organs, such as the sexual lung. Kidneys are present and mostly an urinary cyst. The kidneys are indeed still so amorphous and soft, that they more resemble coagulated blood than an organ, yet meanwhile agree in this respect with the 'milt' and branchial substance.

Abdomen.

The abdomen is not simply confluent with the sexual body, but thrust by it completely forwards. The anus mostly lies in front of the middle of the body.

3314. The intestine separates for the first time distinctly into cephalic and sexual, or small and large, intestine.

3315. The vitelline canal is the cœcum. This is very distinct in the Sharks and Rays.

3316. In Birds therefore the vitelline canal is the cœcum also, and the two cœca, falsely so called, which are placed upon the side of the rectum cannot represent the cœcum coli, or else the Bird must have three of these blind appendages or sacs.

3317. The spleen here appears for the first time; while the pancreas divides into a number of cœcal appendages.

Thorax.

3318. The thorax of the Fish is reduced within very narrow limits; it is like the first thoracic formation, and is thus a Mussel's thorax. The branchiæ with their opercula are similarly formed to the branchial plates and shells of the Bivalve Mollusca. The thorax is therefore attached only externally to the body, and the Fish is to be viewed as a Mussel, from between whose shells a monstrous abdomen has grown out.

3319. But this Molluscan thorax is conjoined with animal systems, and has assumed their noble or elevated type of structure. Here therefore the osseous and sarcose system blend together, and the higher formation of the thorax emerges into view.

3320. For the first time an advance is made towards the formation of a trachea, namely, by the branchial framework or skeleton, which opens into the mouth, and corresponds therefore properly to the larynx. Fishes are therefore the first animals which breathe through the mouth. In all the preceding classes the air entered the body, or the water found access to the branchiæ, by other routes.

3321. They may be termed Mouth-breathing animals, for the first formation of the trachea extends no further than to its junction or communication with the mouth; since, for it to be continued into the head and open self-substantially as a nasal organ, constitutes a second step in advance, which cannot be ventured upon in an Abdominal animal. In Fishes everything relates to the abdomen, and this is expressed by the first union of the trachea having taken place with the pharynx or the mouth.

3322. But, at the same time that the trachea is inserted within the mouth, it opens externally and in the lateral direction upon the body, thus letting the water escape from it posteriorly after a mussel-like or sexual fashion. Thus, the trachea is not yet closed inferiorly, nor hence also the thoracic cavity. Between the head and abdomen there are still openings—branchial foramina.

3323. The trachea is itself, however, a thorax upon a small scale, consisting as it does of rings, or as it were ribs. These arches are not yet united by muscles with each other, and the water flows out between them into the apparent thoracic cavity, from which it next escapes beneath the branchial operculum.

3324. These tracheal rings are the branchial arches. The branchial vessels are tracheal and by no means pulmonary vessels.

3325. Thus, upon taking a retrospective glance at the matter, we may fairly conclude that the branchiæ of the Dermatozoa are not equivalent to the lungs of the higher animals, but are only the antetypes of the bronchi, being thus cervical organs.

3326. The trachea is thus formed prior or antecedently to the lungs, but is still membranous and devoid of any continuous connexion between its rings.

3327. The lung is an organ extraneous or foreign to the trachea, and becomes only as if accidentally associated with it.

3328. But a Sarcozoon is not devoid of lungs nor of aerial respiration; for, being the totality of all lower animals, it consequently unites in itself the respiratory apparatus of the Branchial and Tracheal animals; thus gills and lungs.

3329. In the Fish the first lung appears, that is to say, if we designate or interpret the respiratory organ in Insects only as tracheæ, which do not open into the mouth.

3330. The Fish's lung is the air-or swim-cyst.

3331. The lung is still subordinate to the abdomen and intestine. It is therefore still separated from the trachea or the branchial arches.

3332. Fishes swallow the air and drive it into the pulmonic cyst, where it is analysed or decomposed.

3333. This lung, so soon as it stands opposite to and enters into conflict with a branchia, is what serves to direct or control the action of the heart. It is only when the swim-bladder is allowed to hold good as lung, that the circulation in Fishes admits of being understood. For otherwise venous blood must flow into the heart, from this into the branchiæ, from these directly into the aorta, and so to the different organs without again entering a cardiac cavity, a structure which occurs in no other class of animals, but rather in every instance its reverse. The first heart is arteriose, not venous in all animals, even in the Mussels and Snails and in the embryos. Now, the Fish is still such an embryo, and has only an arteriose heart.

3334. Thus, the following is the "modus operandi" of the parts in question; the swim-bladder is the lung, in which, seeing that it contains air, the blood is oxydized; this oxydized blood flows into the heart and renders it arteriose in character, despite the concomitant influx of venous blood into that organ. Upon this, the blood passes out of the heart through a true aorta, which is called the branchial artery. Instead then of this aorta giving off only some twigs as bronchial vessels to the gills, and next proceeding to pursue its course as a main trunk through the body and along the back, it passes wholly to the branchiæ, i. e. it entirely becomes a bronchial vessel, is slightly oxydized, and then returns upon itself to form the aorta, which should have taken its course directly from the heart.

Senses.

3335. In accordance with the thorax, the corium or true skin is developed. It is mucous in character and muco-secernent like the intestine, from its being constantly in the water. The whole skin is undermined by mucous canals and perforated by their excretory apertures. These foramina of the lateral line are arrested, and metamorphosed branchial foramina, which have only retained the evaporative function of respiration.

3336. The remnants of the tegument's annulation are the scales. They are desiccated air-branchiæ, alary opercula or elytra, and consequently indicate that feature of the Insect, which has continued to work its way into the class of Fishes.

3337. Like the skin, so are the limbs—tegumental members. What is flesh and bone upon them, has kept quite close to the body, and that only which is designed for splitting into digits projects, constituting tegumental digits with cartilages—fins. These fins are something better than the lateral papillæ of the Worms, are furnished at their base with joints, and are in number only four, but crippled or stunted in every possible way.

3338. The fin-rays do not correspond to the digits, but to the nails. They are fibrillated nails, like the wing-feathers of Birds.

3339. Lastly, the head possesses all the organs of sense which belong to a head, but they are still far removed from their perfect condition.

3340. As the nervous system is the first mass, from which the remaining ones have been set free, so also is the nervous sense the first after that of the tegument, which appears as a whole, and serves as a pattern for the subsequent senses. The eye is the sense which is first developed most perfectly, not directly as regards its own completeness, but when considered in reference to the others.

As the sense of feeling has been at once manifested in the vegetative animals as a peripheric nervous sense; so antithetically or vice versâ it is in the higher animals the light-sense, as being the central nervose sense, which appears.

3341. Hitherto both these senses stood altogether alone with each other upon the stage of animal existence, in order, as it were, to play their parts in mutual consent; but so soon as the sense of feeling became individualized into tactile organs, then also the eye made its appearance in a detached or isolated manner.

3342. The Fish's eye is upon the whole composed of the same structures as in the Mammalia; but it is devoid of motion and external coverings.

3343. The ear, as being the sense of motion, has scarcely withdrawn itself from the brain, has not yet become a true external organ, and that portion of it which appears externally, is subservient to inferior systems, such as the branchiæ or gills.

3344. The external auditory organ has become confluent with the branchial aperture, and the auditory ossicles have become parts of the branchial operculum.

3345. In the internal ear only the three semicircular canals have been left. The cochlea is not yet developed.

As true palpebræ or eyelids are wanting to the visual organ, so also are the conchs of the external ear.

3346. The nostrils exist, because a vertebral canal, which terminates in them, is present; stoutly-developed olfactory nerves are also present, so that the sense of smell cannot be wanting. Only this sense has not yet taken the respiratory organ into communication with itself, and both therefore live for themselves in an arrested or stunted condition. This nasal organ does not open into the mouth, admits of neither water nor air passing through it, and therefore serves not as a test-organ to the respiratory process. This is my main point for distinction of Fishes from Reptiles.

3347. Every Sarcozoon, whose nostrils do not open into the mouth, is a Fish. The Siren therefore does not belong to the present class, while the Lepidosiren, having an imperforate nasal organ, does.

3348. The tongue has remained rather an organ of touch and deglutition, than an instrument of taste. The salivary glands are scarcely developed.

3349. But the tongue here appears for the first time in the animal kingdom as a perfect organ provided with muscles, and a lingual bone, as in Man; Fishes are, as regards the development of this sense the Glossozoa, Lingual or Tongue-animals.

3350. As Fishes are the repetition of the intestine and vitellus, so they may be termed abdominal or rather Pelvic animals. They are an abdomen, unto which are appended branchiæ, fins and head.

They are the repetition of the Infusoria, Mussels, and Worms; in them we meet with mucus, branchial opercula, articulated filaments, and labial cirrhi or palpal organs.

Class 11. Myozoa, Rhinozoa.

3351. Those Sarcozoa which for the first time obtain true muscles and a perforated nasal organ are the Reptilia.

3352. True muscles are red, have a definitely circumscribed outline, and are divisible into head, fleshy portion or belly, and tail or tendon. As such they are found for the first time in Reptiles.

Thorax.

3353. With the osseous system in Fishes the sexual abdomen was chiefly developed; with the muscular system therefore, as in the present class, the abdomen proper or intestinal abdomen becomes perfectly developed, and the thorax more spacious in calibre.

3354. The thorax is still blended with the abdomen. In Fishes the disposition was already stirring to create for themselves an air-organ; only this was imperfectly attained, since the swim-bladder communicated with the gullet, but not with the branchial arches or larynx, nor with the nasal organ, as in the present class.

3355. Now, if the swim-bladder be symmetrically developed, if it communicates with the branchial larynx and opens through the nose, the aerial respiration is completely attained, and shares its dominion over the body along with the digestive function.

3356. A Fish, respiring through the nose into two swim-bladders, is an Amphibious animal, a Reptile.

3357. In the Reptile, however, the thorax is still subordinated to the abdomen. Its lungs traverse the whole abdominal cavity, and its manner of breathing is still similar in character to the abdominal function. The lungs are simply two membranous bladders, like two intestines, and admit also of being voluntarily filled with air like the intestine is with water. This filling or inflation of the Reptile's lungs takes place also by the abdomen being expanded at the same time that the mouth is closed by the muscles of the fauces, and is therefore a true process of deglutition.

3358. Their inspiration is still therefore fish-like in character, excepting that the air is drawn in by the nostrils; the respiratory process, however, and the respiratory organ is constituted as in the perfect air-breathing animals.

3359. Reptiles may therefore be called Abdominal animals, while the Fishes are Pelvic animals.

3360. The metamorphosis of the branchial arches into larynx is placed beyond doubt in the Reptiles. The anterior branchial arches frequently unite with the lingual bone, whereby the latter obtains several cornua.

3361. The thyroid gland also makes its appearance here for the first time, while the branchial vessels separate from the arches. Fishes have therefore no thyroid gland.

3362. The circulation is complete. The venous and also the arterial blood enters the heart. But both kinds of blood are still mingled with each other as in Fishes. Yet already, through the direction and arrangement of the cardiac orifices, provision seems to be made for their separation.

3363. The rationale of this mixture of the blood appears to reside in the fact, that many of these animals, and probably all of them in the ovum state, breathe by branchiæ. (This proposition, which was announced in the 1st Edition, 1810. § 305, and there based upon the transitional stages traversed by the animal classes during embryonic development, has since then been raised to a state of certainty.)

3364. The mixture of the blood takes place through an opening in the septum separating the two cardiac ventricles, and which corresponds to the foramen ovale of the fœtus. The heart of Reptiles is therefore a persistent fœtal heart.

3365. Without doubt, however, the arterial blood only enters the left heart, while the venous remains in the right, to be thence driven into the lungs.

3366. In other respects the foramen ovale is not a true opening, but a bifurcation of the vena cava, one branch of which passes into the right, the other into the left ventricle, as I have demonstrated in the 'Beyträgen zur Anatomie' (Frankfurt bei Wesche), in treating of the calf's heart.

3367. There are generally no foramina in the body, but only fissures without orifices.

Abdomen.

3368. The digestive organs are pretty similar to those in Fishes, as is exemplified by the intestine, liver, and spleen; the digestive process is, however, more energetic, and frequently aided by venom or poison.

3369. The sexual parts are perfect. The first true testes and ovaria have originated. The tegumental formation has consequently passed over at the extremities into a glandular, because the vascular system preponderates. Even in the highest Fishes, such as the Rays and Sharks, the testes and ovaria are still not developed to the extent which they are in Reptiles.

3370. In the female the oviducts pass together as complete cornua into an uterus. In the male the seminal ducts are still indeed separate, yet the two bodies or crura of the penis are frequently developed, and continue separate in the Serpents and Lizards, but are connate in the Tortoises.

3371. The kidneys are distinct and symmetrical; their ureters usually unite into a large urinary cyst. Thus, the sexual lung is also significantly developed.

3372. Many of these urinary cysts split, as in the Tortoises, into two cornua. This is the form under which the bladder again occurs in Birds, where its two cornua have been incorrectly termed cœca, but the urinary bladder rectum, because the intestine opens into it.

3373. In Reptiles also there is a cloaca or sexual orifice, into which all the sexual apertures meet together.

The ova of Reptiles possess a vitellus and albumen, and are surrounded by a membranous or sometimes by a calcareous shell.

3374. Hence Reptiles have originally also a cœcum, but it has for the most part disappeared; like its antetype the vitelline canal, which is so small in most Fishes and Birds, as to be scarcely distinguishable.

The tail projects from the body, and is rather trailed after the animal, than enabled to assist the body in its motions, as in Fishes.

Senses.

3375. Many Fishes have only a vertebral column without lateral bones; in the Thoracic animals this deficiency can hardly occur any longer, although we are not, on the other hand, to expect any great amount of perfection to be attained by these parts. Reptiles have osseous ramules, whether such be ribs or true feet; the Serpents have indeed only ribs, but these exist in great numbers; in the Frogs, on the contrary, ribs are wanting, but they have limbs.

In no Reptile do fin-rays occur; consequently, there are no peculiar bones as in Fishes.

3376. In Reptiles the limbs themselves are in a varied or undetermined state, although they constitute a class in which the formation of true muscular limbs is decided. In Reptiles the toes appear for the first time.

3377. As regards the tegument, it quite corresponds with that of the Corals, Snails, and Crabs, of which the Reptiles are a repetition. In some cases it is slimy and naked; in others Mussel-shells originate, as in the carapace of the Tortoises; the scales, scutes, and claws of Serpents and Lizards repeat the rings and scutes of Crabs.

3378. The head has separated itself more from the thorax, the eyes and ears being much more perfect; as regards the latter organs the cranium is always perforated, in the former there are eyelids.

3379. The eyes have still no power of free motion, and the eyelids are as yet very imperfect. It is principally the lower eyelid which closes, while in Mammalia the upper one is the most developed.

3380. The external auditory meatus is notwithstanding usually covered by integument, the auditory ossicles are mostly blended into one, which projects above the skull; the cochlea is wanting.

3381. Reptiles produce sounds for the first time through the lungs; they have voice, but as yet no song.

3382. The nose, however, gives the finishing touch to the head. It has not only opened as a vertebral canal in front, but also as a thoracic cavity posteriorly into the mouth, which was not the case in Fishes. The open nose is the æsthetic character of Reptiles, just as the red muscles are the characteristics of the anatomical systems. The Reptiles are Rhinozoa.

3383. The tongue takes a higher rank than in Fishes. It is throughout soft, fleshy, and smooth; but in most species is still slit into two, which reminds us of a similar condition of the penis.

3384. The teeth are in these animals more like digits than in Fishes. While here they consist for the greatest part of front teeth, and are therefore associated with the intestine, in Reptiles they are mostly lateral, and thus true maxillary teeth, which are annexed to the salivary system. With this special dental formation the saliva is also more active; it is a rapidly fatal poison.

3385. The poison-teeth or fangs have likewise a groove, which can be regarded as the continuation of the salivary duct.

Class 12. Neurozoa, Otozoa.

3386. Those Sarcozoa, whose nervous system is for the first time perfectly developed, and whose ear is open externally, are the Birds.

3387. The completion of the nervous system is the brain; now the brain defines or determines the head; the Bird is, properly speaking, the first Encephalic animal.

3388. In the Bird the head has for the first time, and that indeed suddenly, freed itself from the trunk, and been placed upon a long neck, far removed from the thorax. In no class are there such long necks and so many cervical vertebræ to be found as in Birds. They can be therefore called also Cervical animals, as the neck is not simply present, in order to render the head independent or self-substantial.

The caudal vertebræ, on the contrary, are lessened throughout the Birds, to a degree met with in no other class of animals.

3389. The brain separates for the first time completely into cerebrum and cerebellum, begins to exhibit convolutions, and has in general most of the individual parts analogous to those in the Thricozoa. They are therefore Encephalic animals, which the name of Neurozoa will properly enough imply. The nerves are in comparison with the spinal cord much thinner than in Reptiles and Fishes.

In the Bird also, all the spiritual or mental faculties make their appearance for the first time and suddenly, whereas in the preceding classes but slight traces of them were observed. Such for example are their mechanical instincts, varied modes of nidification, powers of imitation, susceptibility to instruction, knowledge of their benefactors, sentiment of joy, wheedling or coaxing manners, and so on. We have no example of Fishes and Reptiles having learnt any artificial tricks.

3390. Birds are the closest repetition of the Insects, but stand remote from the Crabs and Acalephæ, indications of which are reflected by their structure, disposition, mechanical instincts, and in their nests.

Thorax.

As the sexual body with the tail predominates in Fishes, and the abdomen in Reptiles, so does the thorax in Birds. The whole abdomen and sexual body has been subordinated to the thorax.

The ribs are here directed in such a manner for the first time, that the thorax can act as a voluntary pump-organ. Sternum and respiratory muscles are usually large and peculiarly built.

3391. The lung is only a cluster of Insect tracheæ. They are full of foramina, out of which the air can penetrate into the whole body, exactly as in Insects. In Fishes the lung was still an actual intestine, as seen in the single air-bladder; in Reptiles it was nothing more than a double intestine; in Birds this lung is divided after the fashion of an Insect into aerial vessels or ducts.

In the Bird the intestine lies in the air, and breathes from it, as in the Insect. Birds are also animals which breathe by the intestine.

3392. The whole Bird is lung. Its body is a thoracic cavity, while in the Fish it was simply a sexual cavity, and in the Reptile had obtained the abdominal form. In Birds therefore there is a number of ribs and a strong ossification, from the air itself penetrating into the bones.

Even the intestine has passed over into a motor organ. In Birds and Insects only do we find a true muscular stomach, wherein the food is crushed.

Members or Limbs.

3393. In these animals the formation of limbs or members must be wholly attained. Everything, that works, must work to the production of limbs. The whole body becomes limb.

3394. With the perfected nervous and respiratory system the bones and muscles make also a perfect appearance. The skeleton is hard, complete, and full of air instead of marrow; the muscles are red and separated, the movements free and complex.

3395. The elevated condition of the motor system is demonstrated in the limbs, which here appear in the greatest diversity. There are only two pairs of limbs, thoracic, and abdominal or sexual members. These two are equivalent, so long only as the sexual and abdominal cavity belonging to the trunk proper predominate, and therefore preserve the equilibrium. But the limbs, which have been given to serve the office of the trunk, are destined for progression or swimming, and are simply terrestrial or aquatic members.

3396. The higher limbs are thoracic respiratory members, which are filled with air and clothed with tracheæ, thus exercising a function conformable to the thorax. The thorax has an aerial character. The highest thoracic limbs must be aerial members.

3397. As the abdominal members move upon the earth or in the water, so do the thoracic in the air. The terrestrial limbs are feet, the aerial limbs, wings.

3398. The wings are in the member-formation the extremes of the thoracic limbs. It does not follow from this that they are the noblest in rank, but only that they are the uttermost unto which bodily motion can attain.

3399. The winged animal is the Bird.

3400. The Bird is an Insect with fleshy limbs.

3401. The wings of Birds repeat the alary appendages of Insects in the flesh.

3402. A Bird's wing is a strange but very instructive composition. It consists, namely, of a Reptile's foot and an Insect's wings.

3403. We saw how the branchiæ of the Insect dried up, separated from the feet, and being liberated as wings, were permeated by tracheæ. In the Bird these wings have remained standing upon the feet and been converted into feathers.

3404. A feather is an Insect's wing.

3405. As the Bird grows out at the thoracic limbs into the Insect's wings, so does it upon the whole body into dried branchial laminæ.

The whole body of the Bird is clothed with branchial laminæ or plates.

3406. The wings of the Insects might be called free tracheæ.

The Bird's feathers are Insect-tracheæ. As in the Insect the wings are a leash or net of tracheæ held together by membranes, so feathers are tracheæ dividing into fibre-like ramules.

3407. The Bird is a Reptilian or Frog's body, beset all over with Insects, like as with parasitic animals.

3408. The highest Insect only attains to the possession of four wings, which in some Moths split again into several feathers. In the Bird a vast number of such wings originates.

3409. An Insect's wing is not more than one feather, and is therefore placed also directly upon the body. These wings must multiply so soon as they occur upon a membered trunk, upon arms. Thus, we need not ask why the Butterfly has four, but the Bird only two wings, seeing that the latter is the nobler animal. The discourse cannot be concerning the wings of the former, for the Butterfly has indeed none, but only four feathers.

3410. What the Bird is, it is by virtue of its feathers. It is throughout a trachea, a pair of bellows. Its bones are hollow, full of air, and stand likewise in communication with the lungs; the feather-quills are also hollow.

Senses.

3411. The wings have all the muscles to themselves; the bone has in them gone to ruin. On the legs, on the contrary, the muscles have declined, and the bone has got the upper hand.

Hence it results, properly speaking, that only the thoracic members are perfected, because the Bird is nothing but thorax. The abdomen has, so to speak, vanished, and through this the abdominal limbs are left only, as thin and dry poles or staffs.

3412. From the same cause the muscular flesh upon the head has disappeared. Neck and head are lean, or like Insect horn, which serves only the nervous system.

3413. Beyond the excess of motion the sense of feeling has been nearly lost. The toes are simply destined for motion, and to be used as scrapers, and the digits have become the supports of feathers.

3414. The bill is an Insect's proboscis. In the Bird no teeth whatever project from the flesh, but the jaws themselves. To such an extent has the flesh been withdrawn. What has been called the cere is the only remnant of the facial flesh. Even nostrils and tongue have suffered ossification.

3415. The tongue is a feather. Saliva is scarcely present.

3416. The ears, as being the sense of motion, are far more perfectly evolved than in all the preceding classes. They have opened outwards, and possess an additional auditory part, the cochlea.

With the limbs the sense of hearing must of necessity grow perfect.

3417. The Bird is thoroughly, or "out-and-out" organized as an animal of song. In it Nature attains unto a definite hearing and speech. The Bird speaketh the language of Nature.

With the Bird, the voice, properly speaking, breaks forth for the first time, and that too in a high grade of perfection, as melody.

3418. The ear is the highest representation of the trachea in muscles and bones. The Bird is the Otozoon.

Sexual Parts.

3419. The kidneys are symmetrically constructed, although not yet a perfectly coherent mass. They are of very large size. But a strange feature has come to pass in the urinary cyst, which is the sexual lung. Into this, as has been already said, the intestine opens, and thus it here again passes over into the lung, just as it has passed over into a fleshy cardioid stomach, and completely upwards into the feather-like tongue.

Into this sexual lung the seminal ducts also enter, or the penis, when one is present, along with the oviduct.

3420. The ovum consists of two completely separated substances, and these indeed are so distinct, that the vitellus is secreted at an entirely different place to the albumen, the former in the ovarium, the latter in the oviduct—whereas in Fishes both originated together.

The separation cannot extend further, or else the substances would no longer unite with each other, and the vitellus must be first mixed with the albumen, after it has been completely formed, after or when it is an embryo. In the Bird albumen and vitellus come together during their passage out of the parent's body, or in the act of being laid, and thus before the albumen has been converted into the chick. But in the Mammalia they are first completely united, subsequently to their being laid—i. e. during the period of lactation.

3421. The vitellus is directly secreted from the arteries, but the albumen from an enteroidal sac or the oviduct, which is finally converted into mammary glands.

3422. The vitellus is more a product of the thorax, and is therefore formed directly into the intestine and entire embryo.

3423. The albumen is an intestinal or digestive product, a solution of the organic mass into protoplasma or primary mucus. It is not fashioned itself into the embryo, but is only absorbed as fluid nutriment by the latter.

3424. The shell of the ovum is the last bone, which the animal deposits from the sexual blood, as being analogous to the urine. It is an aerial product, or an analogue of the feather's quill.

3425. Even the nest of the Bird is a spiritual repetition of its plumage, for in it the stalks of plants, tracheæ, or feathers are united into one body, which reminds us in the Swallows of the Acalephæ.

FIFTH CIRCLE. AISTHESEOZOA.

Class 13. Aistheseozoa.

3426. An animal with all its organs of sense perfectly developed, is a Thricozoon.

3427. The nervous system emerges at length freely above the other systems, and it is no longer its mass, but its organs which impart character to the animal. The nervous organs are, however, simply the organs of sense. Through these therefore must the present differ from the preceding class of animals.

3428. Now too the senses first make their appearance in a self-substantial manner above the other organs, serving merely their own functions, and only by chance those of others.

3429. As in Birds the whole body was subordinated to the thorax, in Reptiles to the abdomen, in Fishes to the sex, in Insects to the tracheæ, and so on; in like manner is it here subordinated to the system of the senses or the head.

3430. As the higher senses determine or define the anterior part of the head, and are in their state of perfection provided with muscles; so here the face or visage is invested by flesh, whereby, properly speaking, a true, namely, a moveable countenance, first originates. The Aistheseozoa have a fleshy face.

3431. All possess moveable eyes; fleshy noses, which stand open both externally and internally; ears opening outwards, and mostly provided with a moveable flap; a fleshy tongue, free in front, and moveable lips; with at least thoracic limbs and a skin covered with hairs.

3432. In the Bird, Reptile, and Fish the face is merely invested by tegument, nearly devoid of any muscles, and therefore immoveable. They have a tegumental face, which is incapable of producing any expressions.

3433. In the tegumental face the eyes are motionless, and very rarely both directed so forwards that they can view an object together; the nostrils are frequently devoid of a fleshy rim; the tongue often feather-like, cartilaginous, or covered with teeth; true fleshy lips are wanting, as are frequently the teeth, with even the limbs and digits, or these are divided into a number of rays, forming either feathers, or fins; in the Aistheseozoa there are never more than five toes present, and if there be fewer, then the number admits of being referred to some crippling of the normal quantity, five.

3434. It is remarkable, and serves to the discovery of many laws, that the highest sense here appears for the first time in its state of perfection. The eye in the Aistheseozoa is present in a perfect condition throughout the class, with the exception of the eyelids; the other organs of sense are, on the contrary, exhibited in all their gradations of structure.

3435. It appears, as if the whole animal was first perfected, when the eye is present with all its investment or clothing. The eye of the Aistheseozoa has not simply all its internal chambers and all its humours, but also all its muscles; it is moveable and has perfect eyelids, with very few exceptions—Ophthalmozoa.

3436. The ear now begins to suffer arrest. Its completion is indeed the formation of an external concha or flap for receiving the rays of sound, the hand being repeated in the ear, and its skeleton constituted by the auditory ossicles. This auditory hand occurs only in the Aistheseozoa, and might serve as characteristic if it were not wanting in many, while the eyelids are present. As in the Whales, where the auditory passage can be, however, closed, an act which is not possible in any Bird. The Bird must hear whether it will or no.

In all Thricozoa the interior of the ear is perfect, having cochlea, semicircular canals, tympanum, and, as brachial parts, the three conjoined auditory ossicles. The concha of the ear passes besides through all stages of development, from having a simple margin to one with most varied convolutions, lobes and opercula.

3437. Still more than the ear does the nose undergo modifications. In the Whales it seems to be less adapted for the purposes of smell than of respiration. The olfactory nerves are in them very delicate, and the apex of the nose is destitute of motion.

In other beasts, on the contrary, it is elongated into a very muscular proboscis or snout, and is endowed with the power of voluntary motion.

The form also of the nostrils is very varied, they being round, narrow, patulous, and frequently capable of being closed.

3438. The tongue is indeed mostly fleshy and soft; yet in many species it is provided with horny points, in others invested by a dense coriaceous tegument, so that it appears to represent an instrument for deglutition rather than gustation.

3439. The lips also are mostly fleshy and moveable; yet in many they retrograde exceedingly and lose their mobility, as is partly the case in the Ornithorynchus.

3440. In most, however, the limbs, especially the toes, are still subject to variation. Their perfection consists in the number five, and in the difference between the two pairs of limbs, as in Man. In the Apes the posterior feet are also hands, which is an imperfection; in the Marsupials there are hands posteriorly but toes in front; in other respects there are generally toes, sometimes five, then four, finally two perfect and two dew-claws in the Ox, and at length only one in the Horse, while the posterior extremities are virtually lost in the Whales.

3441. The dental system, as being the set of maxillary claws, is alone present in its state of perfection in the Thricozoa. They alone have, in addition to the incisor teeth, all the five kinds of teeth that differ from each other in form, namely, canine, false molars, laniary, with second and third true molars, corresponding to the five fingers reckoned from the thumb.

3442. In the dentition of those animals which tear their food the greatest amount of completeness and variety is met with, since each tooth has a different form and function.

In the Bears the molars are uniform in character, and so on through the Apes up to Man.

In the Marsupials they are tolerably similar, as also in the Bats and Shrew-mice.

They are still more alike in the Pig and Horse, and the incisor teeth begin to be wanting in the Ruminantia, e. g. the Ox.

In Mice the canines are wanting, in the Sloths the front teeth, and in the Ant-eaters actually all.

3443. In opposition to the perfect eye the general sense of feeling is developed in the tegument. The tegument which is best developed will be that, which represents a self-substantial organ with all its appurtenances, and thus an organ of touch, whose nobility of rank consists in motion. A skin, which is moveable by means of muscles, must take the noblest rank. A skin with tegumental muscles is an organ of feeling, which is already in some degree subjected to the influence of the will. If tegumental muscles do not occur in all these animals, they still do in most of them.

The production of the most perfect coat or covering is the second step, whereby the tegument ascends.

3444. Hitherto the outer covering of animals was pretty inorganic, consisting either of hollow tracheæ, feathers, or semicavernous scales, coat of mail, or lastly, only mucus. All these organs were only constructed after the type of individual vegetable systems, in greatest part only after the respiratory organ, and were therefore partial in aspect or deficient.

The highest covering must also bear the highest meaning. This is that, which grows out of the sanguinary system collectively, out of the capillary vessels. The capillary vessels of the covering are, however, the hairs. The hair is the most perfect covering of the animal.

3445. These animals are the Thricozoa.

Already the highest birds, e. g. the Ostrich and Cassowary, exhibit feathers which merge over into hairs.

3446. An integument clothed with hair, and self-substantially moveable is the perfection of this organ, it is a fur—Furred animals.

3447. The fur is the peripheric combination of the Vegetable and Animal. The hairs are the highest Vegetable, as being the vascular system grown out of or above the animal, and constituting the fundamental or basi-system of the whole body. The tegumental muscles are the lowest Animal. In the fur consequently the whole animal has been represented, but as a limit set between animal and world.

3448. The tegumental covering also varies. The hairs become scanty in respect of number; instead of them spines, horny rings or scales occur, yet there are always hairs on the belly. In many Whales they seem to dwindle into bristles. In some they have coalesced to form a kind of bark, as in the Stellerian Walrus or Sea-cow.

Thorax.

3449. In all the respiration is aerial; in all there is a true costal structure, and a respiration effected through the motion of the ribs or a pumping action; in all the lungs are filled with cells; in all there is a diaphragm, a larynx, a trachea with cartilaginous rings, and a thyroid gland. But the air no longer penetrates from out the lungs into all the cavities of the body, as in Birds.

Abdomen.

3450. The two intestines, namely, the large and small, are more distinct from each other than in other animals; the cæcum coli is in most distinct; the stomach expanded and membranous in texture, so that it operates simply through chemical influence. Liver, pancreas, and spleen occur in all.

3451. The sexual parts are in every respect very perfect. The penis is present in all, and all have an uterus, fallopian tubes, and separate oviducts. The penis is in many still retracted into a cloaca, and the testes frequently lie within the abdominal cavity.

3452. As in the tegument the parts separate and each becomes self-substantial, the fibre animal, the tegument vegetal, and so on even in the sexual animal. The ovarium, consisting of two parts, now also separates, since one becomes animal, but the other remains vegetal. The albumen-organ becomes animal, detaches itself from the sexual parts, is developed in the self-substantial tegument and called mamma.

The Aistheseozoa are thus also Mastozoa or Mammalia.

3453. This separation of the sexual animal is one of the first characters. The mammæ could never be wanting, because they indicate an essential stage in the development. The albumen-organ becomes an organ of sensation. If the existence of mammary organs be doubtful, as in the Ornithorynchus, the hairs are in that case perfectly distinct. No Reptile nor Bird can have hairs, because their covering is derived only from a partial system, the respiratory; while hairs are from the general vascular system, which is the foundation of the tegument, of the sense of feeling. The Ornithorynchus is a furred animal, and this would suffice to bring it among the Aistheseozoa, were we even to deny it mammary organs.

3454. Both sexes, male and female, have breasts. In youth they are most readily detected in the male, because their sexual parts then rank nearer to the female. In other respects the mammæ are probably the chiefest organs of absorption for the embryo.

3455. The mammæ are nobler in rank, when, as udders they become self-substantial; and the more they remove from the belly or abdomen, and come, as breasts, to be placed upon the chest.

D. ORDERS AND FAMILIES.

3456. Had the names been given in strict accordance with rank; then the class-divisions, which correspond to the circles, would have been called Orders.

3457. Families would be class-divisions, which correspond to the classes themselves.

3458. In no class therefore could there be more than four orders admitted, or five, if the sensorial organs be reckoned to constitute a special circle.

From the same reason there are no more than thirteen or seventeen families.—These names cannot meanwhile be so strictly adopted, because the classes are not of equal rank, as has been observed; on this account it is necessary to shove in here and there other divisions, which should be termed at one time Cohorts, at another, Alliances.

3459. If the animals of a class differ from each other, it is only possible by their bringing to bear in addition to their characteristic organ some other organ, and consequently becoming similar to an earlier or later class.

3460. Yet nevertheless in this ascent the animals could never outstep the confines of their own circle. There can be no Dermatozoon which could have bones; for in that case it would be an Osteozoon, and belong to another province.

Every class therefore comprises as many orders only as there are circles with which it comes into contact. Thus in the first circle there is only one order, in the second two, and so on.

Each class therefore includes also as many families only as the circles which are touched by it contain classes. Thus the first to the third class has three, the fourth to the sixth, six; the seventh to the ninth, nine; the tenth and so on, thirteen.

3461. The serial arrangement of animals into families is naturally difficult; but in Physio-philosophy we have to treat not about the execution of the Systematic in detail, but concerning its principles.

FIRST CIRCLE. INTESTINAL, OOZOA—MUCUS-ANIMALS.

First Class.

Gastric, Vitelline Animals—Infusoria.

3462. The Infusoria admit of being reduced to three divisions: the lowest of which, such as the Infusoria proper or Monades, are provided for the most part with cilia; the next in succession, as the Rhizopoda, possess extensible processes, and are mostly covered by a multi-chambered shell; lastly, the most perfect Infusoria have all kinds of internal organs, and especially what has been called rotatory apparatus, as being the dawn of future tentacula.

3463. These three Families obviously correspond to the three classes of the present circle, and that indeed as follows:

To the first class, or Infusoria proper, correspond the Monades.

To the second class, or Polyps, the Rhizopoda.

To the third class, or Acalephæ, the Rotifera.

3464. The Monades are obviously the simplest organized creatures, being mucous vesicles, which move, obtain their food by stirring up vortical currents in the water, and emit what is undigested again by the mouth.

3465. They occur very abundantly in all infusions, and can very well originate, like Fungi, by division of the organic mass, although they are in a condition to propagate themselves, i. e. by spontaneous division.

3466. The Monades are the semen of the animal kingdom, which is dissolved in, or rather produced from, the sea.

3467. The animal body is nothing else than a compound fabric of Monads.

3468. Decomposition is a separation into Monads, a retrogression into the primary mass of the animal kingdom.

3469. All propagation, even that of the sex, commences like the animal kingdom, or with its first family. On that account the embryonic development must be a passage through the animal kingdom.

3470. The Rhizopoda usually adhere together within a multi-chambered calcareous shell, out of which they protrude mucous filaments, and are therefore the antetypes of the Corals or Polyps.

3471. The Rotifera exhibit all kinds of viscera, such as intestine and ovaries; besides what have been called rotatory organs, which remind us of the arms or tentacles of the Acalephæ.

3472. The families of these animals may be therefore aptly named as follows:

Fam. 1. Typical Infusoria—Monades; cilia or vibratile organs. 2. Polypary Infusoria—Rhizopoda; extensible processes. 3. Acalephan Infusoria—Rotifera; intestine and oral organs.

Second Class.

Intestinal, Albuminous Animals—Polypi.

3473. The Polyps also do not admit of being divided into more than three families. The first are only tubes or vesicles with capillary tentacula around the mouth, as the naked Polyps, Tubulariæ, Sertulariæ, and Cellulariæ.

The others have true ciliated tentacular rays surrounding the mouth, and are always condensed inferiorly into a horny, and occasionally stony axis or stem, as is seen in the Gorgoniæ, Alcyoniæ, and Isidiæ.

The third have ordinary tentacula, occurring in great numbers like tassels or tufts around the mouth; their integument is either hardened into stone, or becomes fleshy, as in the Star-corals and Actiniæ.

3474. There is no doubt that the naked Polyps are closely allied to the Infusoria, and among them indeed to the Rotifera, so that they represent but a higher stage of these creatures, characterized by superior size and by tentacular in place of ciliary or vibratile hairs.

3475. The Cellulariæ cannot be more distinctly characterized than by saying that they are cortices or ramules inhabited by Vorticellæ. Thus they are Vorticellæ surrounded by a shell, and may be compared to ova, in whose coriaceous or leathery shell calcareous granules are blended, as in the eggs of the Crocodiles and Tortoises.

3476. They increase by means of ova and by ramification, if the former mode of division is not carried too far.

3477. The tubes of the Tubulariæ appear to be nothing else than the posterior extremity of the Polyp, desiccated or dried. These tubes are not therefore the product of an excretion, but the body itself.

3478. On the contrary, the tubes of the Sertulariæ must be held as being a tegumental excretion, within which the Polyp ramifies and produces ova-cysts. If the naked Polyps resemble ova which are devoid of shells, such as the roe or spawn of Fishes, then the Sertulariæ resemble ova surrounded by a tough skin, like those of Rays and Serpents.

The Radiated Polyps or Horn-corals are invariably ramified and converted towards their interior into a common horny or stony mass; so that the animals themselves appear to have coalesced upon this into a common tegument or bark. They possess a stomach and ovaries surrounding it, which open into the border of the mouth between the rays. They thus increase by ova and ramifications.

They therefore represent the class proper of the Polyps.

The tufted Polyps comprise the proper Corals or Lithozoa, are in form and substance like the Acalephæ but with this difference, that the covering is mostly lithoidal, while in many Acalephans, as the Porpitæ, it only appears as a cartilaginous disc or plate.

3479. These Corals are true ova, having a perfect calcareous shell, like that of the Bird. The gelatinous animal which adheres within a wide-mouthed Madrepore, e. g. Fungia, resembles a vitellus just hatched, and from which the fœtal envelopes have been developed.

3480. The numerous tentacular filaments surrounding the wide mouth resemble the shags of the chorion, which accumulate around the orifice of the umbilical cord to constitute a placenta in the higher animals.

The Corals are brood-eggs inclosed within the uterus of Nature or in the sea. The Coral-animals are an umbilical cord, treasured up for the embryo, while the Tubulariæ are only membranous vitelli, and the Gorgoniæ, ova with desiccated albumen.

3481. The families of Polyps stand therefore in the following order of significance:

Fam. 1. Infusorial Polyps—Tubulariæ. 2. Typical Polyps—Alcyoniæ. 3. Acalephan Polyps—Actiniæ.

Third Class.

Absorbent, Involucral Animals—Acalephæ.

3482. The Acalephæ also can only be brought under three divisions, viz. Röhrenquallen, or Physaliæ, Rippenquallen or Beroes, Hutquallen or Acalephæ.

3483. The Physaliæ are without doubt the lowest, being only giant Infusoria; the Beroes are allied through their simple bodily cavity, to the Gorgoniæ; the Acalephæ, through their form, to the Madrepores, especially the Actiniæ.

3484. They range therefore in the following order of significance:

Fam. 1. Infusorial Acalephæ—Physaliæ. 2. Polypary Acalephæ—Beroes. 3. Typical Acalephæ—Acalephæ.

3485. The first have not yet attained to the unity or single character of the mouth, but imbibe their food through numerous tubes. They are bundles of ramified Vorticellæ, a thoracic duct full of glands and roots, which absorbs nutriment out of the sea, instead of an intestine.

As the first family they are the antetypes of the Mussels and Entozoa, and especially of the Hydatids and Tape-worms, and we shall not be far from hitting the mark, if we compare their air-bladder with the hindermost cystiform member of the body in the Hydatids.

3486. The second family have a single mouth and ribs mostly full of lamellæ, which are probably the antetypes of gills; they are also frequently traversed by nutritive vessels.

They are antetypical of Snails, being in form an abdominal pouch, in substance a liver, and frequently possessing paired tentacula. Higher up, and they indicate the Crabs.

3487. The third have, as a general rule, one central mouth surrounded by four arms and very numerous vessels, which run from the gastric cavity to its margins, and there mostly elongate into filaments or hairs, being thus true lymphatic vessels, which convey the nourishment directly from the stomach through the whole body, and become on its margin tentacula.

3488. As antetypes of the Kracken they particularly manifest the form of the Sepiæ, or Cephalopods, in the strong and frequently papillated arms that surround the mouth. Gland-like nodes are also developed in the margin of the pileus, but their meaning is as yet doubtful. Upon a higher stage, and they are antetypical of Insects.

Their vascular system forms an exceedingly regular, quaternary net, with branches and ramules ranging opposite to each other, which have been believed to be the vitelline network of the ovum when hatched. These vessels terminate likewise in a common marginal vessel, as in the vitellus.

3489. Viewed as a whole they resemble in form, appendages, and substance the fœtal involucra or envelopes. The upper surface may be compared with the convex back of the envelopes, the lower to the concave funnel of the umbilical cord, and the succigerent filaments or hairs to the shags of the chorion. They are probably elongated by injection, like the so-called legs of the Star-fishes.

The secretion of the ova in four ovaries speaks also in favour of their higher grade of development. They lie in four cavities around the stomach, which also open near to the mouth. Their size also is significantly expressive of their higher position.

Finally, they are of separate sexes. In them is the milt for the first time distinctly displayed, and in the same situation indeed where in other animals the ovaries are.

3490. Hence, in these three classes there are found no more than three families, which together make up only one order. The want of a fourth family and so on, proves that the development of these animals does not pass over into the succeeding circle. Their body therefore is only an homogeneous, transparent mass, variously excavated and perforated, but not separated into two cysts, namely, tegument and intestine, and without the other viscera, which are formed by the vascular system, such as the liver, kidneys, and salivary glands.

SECOND CIRCLE. VASCULAR, SEXUAL ANIMALS.

3491. These animals will both traverse the three classes of their circle, as also repeat the preceding three classes, and they consequently divide into two orders and six families.

Fourth Class.

Venous, Ovarial Animals—Mussels.

3492. The Mussels or bivalve Mollusca resolve themselves into two orders, according to the structure of their mantle or respiratory sac. It is either closed in a tubuliform manner, and opens posteriorly into two mostly tubular-shaped respiratory apertures, and in front has an orifice for the passage of the foot—Camacea (Lochmuscheln); or it is slit along its whole length anteriorly; and the pedal aperture is confluent with the anterior and also indeed with the posterior respiratory opening—Ostracea (Spaltmuscheln.)

The first order still represent the cystic form of the Oozoa, and partly by tubuliform calcareous shells placed around the two ordinary shell-valves; but the second, by the freer development of the organs, represent the animals of their own circle.

Order 1. Protozooid Mussels—Lochmuscheln.

3493. These animals repeat the Mucus-animals; are tubular in form, and mostly provided with two long respiratory tubes.

Fam. 1. Infusorial Mussels—Sackmuscheln or Pholades.

Cylindrical, with a tubuliform mantle almost entirely closed and frequently surrounded by a calcareous tube, in addition to the two ordinary shell-valves; the pedal aperture is situated at the oral extremity; the respiratory tubes retractile by means of muscles; the foot is cylindriform.

Of the same kind are the Pfahlmuscheln, Teredines, and Sandmuscheln, as also the Solenidæ. They typify the Nudibranchiate Snails and the Salpæ.

Fam. 2. Polypary Mussels—Klaffmuscheln or Tellinidæ.

Body flat, mostly discoidal; there is a large fissure on the abdominal side of the mantle for the passage of the foot, while posteriorly there are two long respiratory tubes with retractor muscles. Here belong the Tellinidæ and Venusidæ.

I have shown, that they are already to be recognized by the uncinate or hook-shaped groove for the mantle in the shell, and which proceeds from the insertion of the retractor muscles. The foot is usually lancet-shaped. They typify the Patellæ and Ascidiæ.

Fam. 3. Acalephan Mussels—Cardiacea.

Body globular in form, mantle having a pedal slit on the abdominal side; two respiratory apertures without retractor muscles; foot mostly uncinate or strap-shaped.

T have shown that these creatures are to be recognized by a discoid groove in the shell, which simply depends upon the mantle, the retractor muscles being wanting. Here belong the Cardiacea and gigantic Chamidæ, in which last a byssus occurs, and the union also of the two occlusor or sphincter muscles, as in the following order. They antetypify the air-breathing Snails and Cirripedia.

Order 2. Conchozooid Mussels—Spaltmuscheln.

3494. These animals represent their own circle.

The pedal slit in the mantle occupies the whole length of the latter, and is confluent with the anterior or also with the posterior respiratory aperture; so that only one or even no aperture is left, and this when present is besides never elongated in a tubular form; the retractor muscles are therefore wanting also, and the shell simply exhibits a discoid groove for the mantle. The occlusor muscles approximate and unite at their terminations. Both usually coalesce into one.

Fam. 4. Typical Mussels—Mytilaceæ.

Occlusor muscles separate, and mantle slit to such an extent, that only the posterior respiratory aperture remains; foot mostly tongue-shaped or coniform, with occasionally a byssus.

Here belong the fresh-water Mussels and the Mytili proper, of which last many bore into rocks. They typify the Capulidæ and Brachiopoda.

Fam. 5. Snail-Mussels—Arcaceæ.

Have two separate occlusor muscles and a perfectly separate mantle without respiratory aperture; the foot small, mostly cartilaginous. Here belong the Arcæ, Aviculæ, and Pearl-mussels.

They typify the Trochidæ and Pteropoda.

Fam. 6. Kracken-Mussels—Ostracea.

Only one occlusor muscle, mantle entirely open or slit, so that both respiratory apertures are only oblique incisions therein; foot very small, frequently furnished with a byssus. They typify the Buccinidæ and Cuttle-fish.

Fifth Class.

Arteriose, Orchitic Animals—Snails.

3495. The Snails likewise divide into two orders, according to the two circles, preindicated by the Ovum-and Sexual system. Their branchiæ are either ramulate or pectiniform, the sexual parts combined or separated.

The first kind are still frequently gelatinous in texture, transparent and naked; their branchiæ usually stand out freely as filaments, lamellæ, or ramules upon the back, or lie simply as a vascular network within the mantle. All are androgynous. They therefore obviously repeat the Protozoa or Mucus-animals.

The second are invariably covered by the shell and by a mantle, within the cavity of which the branchiæ lie concealed as one or two comb-like bodies. Tentacula and eyes, which are occasionally wanting in the preceding order, are here universally present; the sexes separate.

As in the Snails, the male parts make their appearance for the first time distinct and individualized, and are also a characteristic organ of the class; so also do they serve as bases of division, and the Snails may be divided into those which are Androgynous or bisexual, and those with separate sexes, i. e. Diœcious.

Order 1. Protozooid Snails—Androgyni.

3496. The male and female sexual parts united together in a single individual, branchiæ ramuliform, occurring either as filaments, leaflets or ramules, freely situate upon the naked body, or as a network lodged within the pallial cavity and surrounded by a shell.

The Nudibranchiate species live in the sea, those with hollow branchiæ or the Pulmonea in the air; the former feeding mostly upon animals, the latter upon plants.

Fam. 1. Infusorial Snails—Notobranchiata, or Tritoniæ.

Body gelatinous and membranous, cylindrical and naked, devoid of shell, with branchial filaments or ramules disposed in two rows upon the back.

Here belong the Tritoniæ and Dorides. Their body is muscular; the tentacula not retractile; the male sexual parts open in company with the female upon the right side of the neck, as in the higher organized Snails. All inhabit the sea. They prefigure or typify the Salpæ.

Fam. 2. Polypary Snails—Pleurobranchiata, or Patellæ.

Body and sexual parts as in the preceding family, the branchiæ, however, occurring as ramules or leaflets upon the sides of the body, are more or less covered.

Here belong the Phyllidiæ, Schüssel-and Schildschnecken. They are the antetypes of the Ascidiæ.

Fam. 3. Acalephan Snails—Dictyobranchiata or Limacidæ.

The branchiæ form a rete or network within the pallial cavity, and respire the moisture of air; mantle and viscera are mostly surrounded by a shell; the body is therefore bipartite, being separated into a splanchnic or visceral body and a foot with head.

Here belong the Air-breathing Snails, both land as well as fresh-water species. They typify the Cirripedia.

The shells are mostly thin and horny, yet nevertheless contain a considerable quantity of calcareous earth, and are mostly devoid of opercula.

Those species, which dwell in fresh water, do not possess introvertible tentacula like the marine Snails, and the eyes are placed at their basis; the sexual orifices are separate.

In the Land-snails, the tentacula are introvertible, and support the eyes upon their apex; the sexual apertures are blended into one. The former, like the marine Snails, lay numerous small ova inclosed within a gelatinous mass in the water; the latter deposit their ova free, covered with a membranous, and occasionally calcareous shell, in the earth. Copulation is effected in all by a reciprocal interchange of the androgynous species.

I have observed that individuals of Limnæa auricularia can continue to propagate for several generations without being impregnated; they must impregnate themselves.

Order 2. Conchozooid Snails—Diœcii.

3497. Branchiæ situated within the cavity of the mantle, and hanging down in the form of a comb; shell for the most part spirally contorted; sexes separate—Pectinibranchiata.

Here belong the Capulidæ, Turbinidæ, Neritæ, Conidæ, Volutidæ, Buccinidæ, Muricidæ and Strombusidæ.

The tentacula are not retractile, and have the eyes mostly seated at their basis; the penis is external, very large, and cannot be drawn within the body, but is only reflected into the pallial cavity; most of them have a protrusile perforating proboscis, and an operculum. They lay numerous small ova, contained within large membranous cases, which frequently hang in rows to each other like a necklace of pearls. The shells are in some instances horny, in others of a stony texture.

Fam. 4. Mussel-Snails, Capulidæ.

Only one branchial comb within the mantle, and covered merely by a flat hood-shaped shell; no operculum.

Here belong the Capulidæ; all the species are marine. They prefigurate the Brachiopoda.

Fam. 5. Typical Snails, Turbinidæ.

Two branchial combs, mantle devoid of a respiratory groove, shell turbinated; mostly furnished with an operculum, and that indeed of a stony texture. Here belong the Turbinidæ, and Trochidæ, such as the Cyclostomata, Paludinæ, Ampullariæ, Janthinæ, Neritæ. Live in the sea and in fresh-water.

Fam. 6. Kracken-Snails, Buccinidæ.

Like the preceding family, but their mantle has a groove, and there is a horny operculum. Here belong the Conidæ and Volutidæ, Buccinidæ, Muricidæ, Strombusidæ. Almost all live in the sea and are of sanguisugal habits. They antetypify the Cuttle-fish.

Sixth Class.

Cardiac, Nephritic Animals—Kracken.

3498. Body cylindrical, without sole or foot; frequently venous hearts together with the arteriose hearts, and a kidney-like organ.

Such are the proper Cylindrical Snails, which are either sessile or fixed, or move themselves by fins and what have been called arms—Sessile and Natant Kracken. Here belong the Salpæ, Cirripedia, Brachiopoda, Pteropoda, Heteropoda, and Cephalopoda. They all live in the sea.

Branchiæ and sexual relations very varied.

They divide likewise into two orders, in accordance with the two circles of Mucus-animals and Conchozoa; the former are spathiform, mostly gelatinous, and firmly sessile or fixed; androgynous, without head and rudders or fins. The branchiæ trellis-like and filiform—Ascidiæ, Cirripedia and Brachiopoda.

The others have a kind of head with arms and eyes, or fin-shaped steerage-organs upon the body; branchiæ pectiniform, reticular, and leaf-shaped—Pteropoda, Heteropoda, and Cephalopoda.

Order 1. Protozooid Kracken—Rumpfkracken.

3499. Body sacciform, mostly gelatinous, without head and eyes; species androgynous. They are destitute of independent locomotion, most of them being quite stationary or fixed, and surrounded frequently by a shell; some few float about passively in the sea.

Fam. 1. Infusorial Kracken—Salpæ.

The Salpæ are gelatinous, freely natant cylinders, perforated by an open tube, within which are situated the branchiæ, heart, mouth, intestine, and liver, without any tentacula. They continue to hang for a long time to each other, as though they were in the ovary.

They undergo a remarkable metamorphosis, which traverses two generations, the young meanwhile not resembling the mother but the grandmother.

Body within a sacciform mantle, with two opposite respiratory apertures.

Fam. 2. Polypary Kracken—Ascidiæ.

The Ascidiæ have a sacciform body with two co-approximate respiratory apertures; branchiæ internal and trellis-shaped.

These gelatinous or cartilaginous animals adhere firmly to rocks, with the respiratory apertures directed upwards as in the Mussels, but the branchiæ are not foliiform; the internal cavity is lined with a membranous sac, upon which the branchial vessels are dispersed in a trellis-like manner. At the bottom of and within the sac is the mouth, which is destitute of tentacula. Intestine, liver, and a heart that is simple or undivided. Mode of propagation unknown.

They are frequently connato-sessile, like the Polyps.

Fam. 3. Acalephan Kracken—Cirripedia.

Body sacciform, without branchial openings, oral apertures situated at the inferior extremity of the longitudinal fissure in the mantle, and provided with a kind of maxillary apparatus; above or behind the mouth are annulate or horny filaments representing caudal fins or feet, upon the basal joints of which is a branchial filament. Here belong the Balani and Lepades—Fuss-kracken.

These animals are likewise sessile, at least when full grown, and are surrounded by shell-plates, which remind us of the Echini or Sea-Urchins, whose antetypes they are; this resemblance is particularly distinct in the Balani, which have similar odontoid valves upon the aperture or mouth of the shell. These animals also undergo a metamorphosis, since in the early periods of their existence they swim about like small Crustacea, and later on become fixed or sedentary, and surrounded by the plates of shell.

The Lepades have the ordinary shells of Mollusca, but each of the two valves consists of two pieces, between which an odd one is interposed down the back.

These five shell-pieces become in the Balani a regular set of teeth, which are adherent within the cylindrical shell, by which the posterior part of the body, or the peduncular and elongated mantle, is surrounded. (Vid. Oken's 'Allgemeine Naturgeschichte,' V, 1835, 509.)

They bear a resemblance to the Crustacea, not simply in the annulate horny feet, but also in the double and ganglionic nervous chord lying along the abdomen; only they are androgynous, which occurs in no Crustacean.

Order 2. Conchozooid Kracken—Kopfkracken.

Tentacula upon the head or fins upon the body. They repeat the Conchozoa or Shell-animals.

Fam. 4. Mussel-Kracken—Brachiopoda.

The body is surrounded by a mantle open above, and by two shells; on the sides of the mouth there are two arms.

These animals look exactly like Bivalve Mollusca; they are firmly adherent to rocks, being frequently supported upon a hollow pedicle, which is a prolongation of the mantle. Branchiæ and sexual parts but little known; species probably androgynous—Armkracken.

3500. In the following families the body is free and sacciform, provided with arms or fins, and mostly with eyes upon a kind of head.

These animals have the mouth situated above or in front of the body, and are distinctly separated into mantle and abdomen, while they are frequently surrounded by a shell. They have a kind of head with tentacles or arms, and frequently furnished with eyes like the Snails, or pretty nearly like the Fishes; the sexual parts united and separated. They all row, paddle, or steer themselves about in the sea.

Fam. 5. Snail-Kracken—Pteropoda.

Body mostly gelatinous, sacciform, closed all round and free; fins upon the sides of the neck, with two tentacula frequently projecting from near the mouth; androgynous, naked, and inclosed within a shell.

These transparent animalcules swim about upright in the sea, and wave the fins in this position as rapidly as a butterfly does its wings. Most of them are covered with a spathiform and likewise transparent shell. The branchiæ are placed externally on the body, but are not very distinct. Several species have an appendage in front of the neck, which is obviously a rudiment of the Snail's pad or sole—Flugelkracken.

The Heteropoda appear to resemble the Plantar or Sole-Snails, but the body is mostly gelatinous, and the foot or sole is only compressed to form a fin, so that they can only swim but not creep with it. Many of them have a shell almost like that of the Argonauta. Pterotracheæ—Ruderkracken.

Fam. 6. Typical Kracken, Cephalopoda or Sepiæ.

Muscular animals inclosed within a sacciform mantle, open in front; head furnished with eyes, and surrounded by more than four strong prehensile arms; laminated or leaf-like branchiæ within the mantle, sexes separate; in the body is a nephroidal or kidney-like gland, which secretes a dark-coloured or inky fluid, on which account they are called by us 'Dintenschnecken'—Sternkracken. They are obviously the highest organized Malacozoa, and already remind us strongly of Fishes, partly from their size, partly by their fleshy body, and in part by their perfect organs of vision.

The body is often as large as the trunk of a man; the head being separated from it by means of a neck, has in its interior a kind of cartilaginous brain-case or skull, with externally a pair of jaws resembling a Bird's beak, and with eyes tolerably similar to those of Fishes. Auditory organs are also present, which consist of a tympanic cavity inclosing an otolithe or ear-ossicle; nostrils are wanting. The so-called arms are perfect organs of locomotion, as also useful for seizing the prey, being provided for this purpose with sucking cups, which adhere by producing a vacuum, when applied. In other respects these arms are nothing else but the Snail's sole divided in front into lobes. The ova resemble berries, and hang attached to one another in branched clusters like a bunch of grapes. The Sepiæ possess a remarkable gland, which is complicated with the liver, and secretes a dark brown juice, which has been called ink or sepia; it probably ranks in the significance of the kidneys.

Many are covered with a shell externally, as the Nautili and Argonautæ; but in the common Sepiæ this shell adheres within the mantle upon the back, and forms a straight lamina or plate, which is sometimes horny, sometimes calcareous in its texture. It has been called the "white fish-bone." What is regarded as the dorsal side of the animal is its ventral side, because upon the former lies the pallial aperture and the anus, while the vitelline sac is also inserted there.

In the form of the body, as well as in the circular position of the cephalic arms, the Sepiæ strikingly resemble their antetypes, the Acalephæ and Cirripedia, and their metatypes, the Asteriadæ and Crustacea.

With these animals the second stage or circle through which the Dermatozoa pass, or that of the Sexual animals, is closed. They require only a slight additional grade of perfection, and they would pass over into another class of animals. Thus were the arms to become horny and articulate, they would be Crustacea; had the head a nose, and the body consequently a myelon or spinal chord, they would then be Fishes.

SECOND CIRCLE. RESPIRATORY, CUTANEOUS ANIMALS—ANCYLIOZOA.

3501. Body annulate.

Here range the Worms, Crustacea, and the proper or volant Insects.

3502. In this circle a remarkable relation is revealed. If, namely, its classes, orders, and families be compared with those of the two preceding circles, it is then distinctly shown that the present one again commences quite from below, ascends parallel with both these, and transcends them in its highest inmates or members.

As an example of the first case, the imperfect condition of some Entozoa, and their great resemblance to Infusoria, is sufficiently expressive.

The Worms evidently pass parallel to the Mucus-animals, and the Entozoa indeed to the Infusoria, the Red-blooded Worms to the Polyps, but the Holothuriæ chiefly to the Acalephæ, near which they are still arranged up to the present day, although they are articulated, and have an intestine and vessels.

Thus this class traverses the three inferior classes, and consequently imparts to them only the value of orders, or must itself be raised only to the rank of an order, a step, however, which, considering the great number of Worms, would not be suitable or just. The names may therefore remain for the sake of uniformity; only it must be borne in mind that they are of unequal value.

The same relation is exhibited in the Crustacea or Crabs. They obviously admit of being parallelized with no other animals than the Malaco-or Conchozoa. The Entomostraca and Crabs evidently repeat the Mussels, the Aselli the Snails; but the Spiders and Scorpions the Kracken or Cephalopoda. Consequently here also the orders correspond to the preceding classes.

The true or proper Insects transcend the Sexual animals, and therefore conform to the classification of their own circle, namely, they repeat the Worms and Crabs, and finally mount forth upon their own stage.

The inferior or lower organized animals form consequently two series, viz. the Smooth and Annulate, which in their lower members range parallel, and that indeed after the following manner:

A. Smooth. B. Annulated or Ringed.

I. Protozoa. I. Worms.

a. Stomach,1. Infusoria.1. White-blooded Worms.

b. Intestine,2. Polypi.2. Red-blooded Worms.

c. Absorbents,3. Acalephæ.3. Holothuriæ.

II. Conchozoa. II. Crustacea.

d. Veins,4. Mussels.4. Crabs.

e. Arteries,5. Snails.5. Aselli.

f. Hearts,6. Kracken.6. Spiders.

III. Ancyliozoa. III. Flies.

g. Retia,7. Worms.7. Tracheoptera.

h. Branchiæ,8. Crabs.8. Dictyoptera.

i. Tracheæ,9. Flies.9. Ceratoptera.

The Worms have simply an annulate body with reticular or filamentary branchiæ, but no feet; the branchiæ are supported by the body.

The Crabs have an annulate body with feet; the branchiæ are supported by limbs.

The Insects have an annulate body with feet and wings; the body is supported by the branchiæ.

Seventh Class.

Reticular, Papillose Animals—Worms.

Protozooid Ancyliozoa.

3503. There are Worms with a soft body and white blood, without proper tentacula; others with red blood, with and without tentacula, having also bristles along the sides of the body; lastly, the rings of the body become hard or muscular, and a circle or ring of osseous maxillæ forms around the mouth, which is usually surrounded by numerous tentacula, as in the Star-fishes and Holothuriæ, in whom the blood is nevertheless colourless.

They divide accordingly into three orders, and each of these again into three families, in accordance with the classes, namely, those of the Protozoa or Mucus-animals, through which they pass.

Order 1. Infusorial Worms—Parasites.

3504. The White-blooded Worms or Entozoa are very imperfect animals, a fact which proves that this circle recommences quite inferiorly or from below. They live for the most part in the interior of other animals, being thus located in darkness and in places where they obtain but little oxygen. Their blood therefore is not simply colourless, but even its vessels are only imperfectly developed. They respire without doubt through the tegument. In many, a distinct or separate intestine being wanting, it is the tegument also which digests; in others the intestine is simply a sac without an anus. The sexual parts too are in many species of a doubtful character, while meantime there are both androgynous and diœcious individuals. In the latter the male parts open invariably at the posterior extremity of the body, as in Insects; the female parts in front of its caudal end, as in the Crustacea. Both are in other respects constructed as in Insects, namely, there are two oviducts or seminal ducts, which unite before reaching their external orifice. They divide into three groups.

In one of these the body is tolerably smooth, and the pharynx commencing from a simple suctorial mouth elongates into a ramified intestine without an anus; they are androgynous—Saugwürmer.

In others the body itself supplies the place of the stomach; it is corrugated, and receives the food through one or several orifices, without separating into a special intestine. They have nearly all a claviform proboscis or rostrum, with which they perforate substantial cavities for themselves; it would seem that they are both androgynous and of separate sexes—Hydatids and Tæniæ.

Others are separated into tegument and intestine like the Mussels and Snails, but without having a distinct vascular system, heart, and liver, though provided with a nervous chord and separate sexual parts—Ascarides.

Fam. 1. Monad-like Worms, Saugwürmer.

Body tolerably smooth, suctorial mouth and sucker, the intestine losing itself in the tissue of the body, and without an anus; androgynous.

They remind us through their small size and structure of the Monades, especially the Cercariæ, and among the Worms typify or prefigurate in particular the Hirudines or Leeches, both by their form and power of suction, as also in the ramification of the intestine.

Many Cercariæ might be metamorphosed into Distomata, and so be or constitute their young.

The Planariæ are slightly different from the Liver-flukes or Fasciolæ hepaticæ, since they are white, bloodless, have a ramified intestine without anus, and increase also by fissiparous generation. They belong to the present order, although they live not as parasites, but in a state of freedom.

Fam. 2. Rhizopodoid Worms, Hydatids.

Body annulate or articulate, with a claviform proboscis without an intestine; they appear to have several mouths.

The Cystica develop ova simply upon the internal wall of the tegument; the body's last ring is expanded into a cystic form, and is mostly much larger than the whole body. The Cœnurus cerebralis, or Brain-hydatid, ramifies like the Polyps.

The Cestoidea have in each joint or member of the body an ovarium, and, as it would appear, male parts also, so that they are androgynous. The sexual orifices are at the border or upon the surface of the posterior members. The member can be viewed as an ovarium liberating itself; as in the Lerneæ and Arguli.

The Filariæ or Thread-worms, which also belong here, are in the form of a cylindrical tube, with separate sexual parts, which open posteriorly.

Fam. 3. Rotiferal Worms, Ascarides.

Body cylindrical, intestine free, with mouth and anus; sexual parts separate.

Upon the mouth these Entozoa have some papillæ or points, which may be regarded as tentacula. The larger species have a distinct nervous cord. The Gordius cannot well take any other position than the present, although it does live in a state of freedom.

Order 2. Polypary Worms—Hirudines.

3505. Body cylindrical with branchiæ in or upon the tegument, blood red; two ganglionic nervous threads run along the ventral surface of the body, as in Insects; all are indeed androgynous.

Here belong the Red-blooded Worms, as Hirudines, Lumbrici, Nereides, and Serpulæ.

Fam. 4. Tubularial Worms—Dermatobranchiata.

Body cylindrical. The branchiæ are only a vascular network in the tegument.

Here belong the Hirudines and Lumbrici.

The Hirudines have a perfectly naked body, without filaments and bristles, a perfect network of vessels containing red blood within the tegument, an intestine with an anus, both sexual parts androgynoid; posteriorly they have a pad or sucker; in the mouth there are mostly maxillæ, and upon the head simple eyes.

The Naiades and Lumbrici have bristles in longitudinal rows upon the sides of the body. The latter are androgynous. The Naiades increase by division.

The Thalassemæ have a protuberant white body; red blood-vessels only upon the intestine; mouth rostriform.

These Worms stick in the mud, and are nourished by it. They have here and there bristles, but which do not form any longitudinal rows. They appear to absorb water through the skin, and respire by the intestine. They cannot, by reason of their red blood, range with the Holothuriæ.

Fam. 5. Alcyonioid Worms—Notobranchiata.

Body depressed, with pedal filaments, tentacula and branchiæ in two longitudinal rows upon the back.

These Worms all live in the sea, adhering mostly upright in the earth, and have frequently annulate, rigid tentacula, ocelli, and pairs of maxillæ, like Insects. The gills are not unfrequently covered with pergamentaceous scales, as in many Nereides, and especially in Aphrodite.

Fam. 6. Actinioid Worms—Auchenobranchiata.

Body inclosed within a pergamentaceous or calcareous tube with lateral bristles, branchiæ and tentacula upon the neck or head.

The neck is surrounded by a kind of mantle, almost as in the Snails, so that several animals have been arranged here, which are now known to be veritable Snails. Upon the head many have a horny operculum, whereby they can close the shell.

Here belong the Amphitritæ, Terebellæ, Serpulæ, and Sabellæ.

Order 3. Acalephan Worms—Sternwürmer.

3506. These creatures attain the most perfect structure of the Worms. The blood is white, the form cylindrical, globular and stellate; the mouth surrounded by a ring or wreath of maxillæ. The nerves form a ring around the pharynx, and upon the latter are placed membranous cysts, which spirt water into the tentacula or feet as they have been called, and thereby expand them.

It is impossible for these animals to continue to range with the Acalephæ, although they resemble them in outward form; for they consist of two cysts, the intestine having become freed from the outer one as a special sac; moreover, they have a perfect vascular system, distinct muscles, a mouth with a dental apparatus, which prefigurates a complete skeleton, a peculiar vascular system for the injection of the tentacula or feet, a nervous ring surrounding the pharynx, an ovarium entirely separated, and lastly, a perfectly annulate body.

Fam 7. Physalial Worms, Holothuriæ.

Body cylindrical, very plentifully supplied with muscles. Mouth and anus present, the former of these being surrounded by a dental wreath and ramified branchimorphous tentacula; branchiæ upon the intestine, and branchial aperture at the anal extremity. They correspond to the Physaliæ.

Their tegument is a perfect muscular tunic, consisting of several longitudinal bands, which pursue a downward course upon its internal surface; in other respects being transversely corrugated and full of papillæ, partly replete with hollow podoidal filaments, which by the injection of water into them are elongated; thus, they present a resemblance to the Acalephæ.

Fam. 8. Beroeal Worms, Echini.

Are at bottom Holothuriæ with ossified tegument, or Asteriadæ with shortened rays.

The Echini have an anus, pretty like that of the Holothuriæ, and also similar feet, which are protruded in a similar manner through apertures in the shell. The dental wreath surrounding the mouth is a complete bony framework, which has been called, on account of its form, "Laterna Aristotelis," and bears a considerable resemblance to the valves of the Balani, the antetypes in general of the Echini, just as these are of the Opossum Shrimps.

Fam. 9. Medusal Worms, Asteriadæ.

Body stelliform, consisting of bony rings; contains a free multilobular intestine with blood-vessels and branchiæ; several ovaria; it would appear that they are without male parts.

Here belong the Encrinites, Pentacrinites, and Asteriadæ proper. Around the mouth of the Encrinites and Pentacrinites stand long, ramified, and likewise articulated tentacula, which remind us of the arms of the Acalephæ and Cephalopoda.

Fundamentally too, in the Star-fishes, the disk only is the body proper, and the rays are the tentacula, which, being monstrously developed, surround the mouth; what have been called pedicles upon these, represent the suckers of the Sepiæ.

Eighth Class.

Branchial, Pedal Animals—Crustacea.

Conchozooid Ancyliozoa.

3507. The Crustacea are Worms with horny rings to the body, jointed feet and tentacula, which mostly breathe by branchiæ.

They correspond to the Conchozoa, or Shell-animals, and divide therefore into three orders, each of these including six families.

Here belong the Crabs, Wood-lice, and Spiders.

In the lowest forms the head, thorax, and abdomen are blended together, and the back mostly covered with a great horny scute—Mussel-like Insecta.

In the next place the thorax and abdomen admit of being clearly distinguished, both by their form as well as by their appendages, which are much larger on the thorax, as in the Cray-fish.

Then follow cylindrical forms with numerous feet, appended to uniform rings, but having a head free and distinguished by tentacula, maxillæ, and eyes—Wood-lice.

The Wood-lice bear a resemblance to the air-breathing Insects, although all parts of the body still pass over or blend gradually into each other.

In the Arachnida or Spiders aerial respiration takes place, and their body enters into relations with the more highly organized Insects, since the head becomes small, the abdomen large, thick, and short.

As the Crustacea pass parallel to the Conchozoa or Shell-animals, so do they divide into three cohorts or groups: the Mussel-, Snail-, and Kracken-like Crustacea, or Crabs, Wood-lice, and Spiders.

Cohort I. Mussel-like Crustacea—Crabs.

3508. Head and thorax connate, being mostly covered with a shell or shield, abdomen stunted or caudiform; maxillæ and branchiæ present.

Order 1. Lochmuschelartige, Pfriemenkrebse.

3509. The feet mostly simple and pointed, without large claws or forcipes, and furnished with setæ or lamelliform branchiæ; eyes sessile.

Fam. 1. Pholadoid, Mussel-Insects.

Small, almost microscopical, and slightly annulated animals with an uni-or bi-valvular dorsal shield or testa, stunted maxillæ, and few legs, having attached to them setiform branchiæ.

These animals are found in all stagnant waters, in which they are incessantly paddling or rowing themselves about. They remind us of those Infusoria which, like Brachionus, are covered by a scute or shield. They are what have been called Monoculi (Entomostraca or Lophyropoda), e. g. Daphniæ.

Number of feet small, and beyond their appended setæ there are no branchiæ; two eyes frequently blended together; antennæ mostly furcate like the feet; sexes separate; a perfect circulation within a true Mussel-like ventral cavity. They are microscopic Mussels with eyes and feet.

Fam. 2. Tellinoid, Branchiopoda.

Similar animalcules to the above, but with a body strongly annulated, naked or covered with a double shell, and provided with numerous feet, unto which are attached leaflets that serve as branchiæ.

Here belong the Branchiopoda properly so called.

Fam. 3. Cardiaceoid, Shield-Crabs.

Large animals, with strongly annulated body and numerous feet; head and back covered by a shield, whereupon are the eyes—Phyllopoda.

Here range the Trilobites, Apus, and the Molucca or King-Crabs.

Order 2. Spaltmuschelartige, Scheerenkrebse.

3510. Five pairs of thoracic feet, of which the first pair is mostly large and forcipiform; the eyes upon moveable pedicles or foot-stalks.

These animals usually attain a striking size, and are generally the largest among the horny Ancyliozoa.

The sexual parts open mostly upon the posterior legs.

The abdomen or tail usually supports five pairs of stunted feet, to which the ova hang.

The number of maxillæ agrees tolerably well with that of the thoracic feet.

Fam. 4. Mytiloid, Locust-Crabs.

All the feet of pretty equal length, and the forceps stunted in size; the branchial plates free upon the abdominal feet—Squilla.