Part I. ON THE SEASONAL DIMORPHISM OF BUTTERFLIES. (continued 2)

All the seasonally dimorphic butterflies known to me are found in Hoffmann’s list of Siberian immigrants, with the exception of two species, viz., Euchloe Belemia, which is cited as an African immigrant, and Pieris Krueperi, which may have come through Asia Minor, since at the present time it has not advanced farther west than Greece. No considerable change of climate can be experienced by migrating from east to west, so that the seasonal dimorphism of Pieris Krueperi can only depend on a cause similar to that which affected the Siberian immigrants, that is, the gradual increase of temperature in the northern hemisphere since the glacial period. In this species also, the winter form must be the primary one. In the case of E. Belemia, on the other hand, the migration northwards from Africa certainly indicates removal to a cooler climate, which may have originated a secondary winter form, even if nothing more certain can be stated. We know nothing of the period of migration into southern Europe; and even migration without climatic change is conceivable, if it kept pace with the gradual increase of warmth in the northern hemisphere since the glacial epoch. Experiments only would in this case be decisive. If the summer generation, var. Glauce, were the primary form, it would not be possible by the action of cold on the pupæ of this brood to produce the winter variety Belemia, whilst, on the other hand, the pupæ of the winter generation by the influence of warmth would be made to revert more or less completely to the form Glauce. It is by no means to be understood that the species would actually comport itself in this manner. On the contrary, I am of opinion that in this case also, the winter form is primary. The northward migration (from Africa to south Spain) would be quite insufficient, and the winter form is now found in Africa as well as in Spain.

V. On Alternation of Generations.

Seasonal dimorphism has already been designated by Wallace as alternation of generation,37 a term which cannot be disputed so long as it is confined to a regular alternation of dissimilar generations. But little is gained by this definition, however, unless it can be proved that both phenomena are due to similar causes, and that they are consequently brought about by analogous processes. The causes of alternation of generation have, until the present time, been scarcely investigated, owing to the want of material. Haeckel alone has quite recently subjected these complicated phenomena generally to a searching investigation, and has arrived at the conclusion that the various forms of metagenesis can be arranged in two series. He distinguishes a progressive and a retrogressive series, comprising under the former those species “which, to a certain extent, are still in a transition stage from monogenesis to amphigenesis (asexual to sexual propagation), and the early progenitors of which, therefore, never exclusively propagated themselves sexually” (Trematoda, Hydromedusæ). Under the other, or retrogressive form of metagenesis, Haeckel includes a “return from amphigenesis to monogenesis,” this being the case with all those species which now manifest a regular alternation from amphigenesis to parthenogenesis (Aphides, Rotatoria, Daphniidæ, Phyllopoda, &c.). Essentially I can but agree entirely with Haeckel. Simply regarding the phenomena of alternation of generation as at present known, it appears to me to be readily admissible that these multiform modes of propagation must have originated in at least two different ways, which can be aptly formulated in the manner suggested by Haeckel.

I will, however, venture to adopt a somewhat different mode of conception, and regard the manner of propagation (whether sexual or asexual) not as the determining, but only as the secondary cause. I will further hazard the separation of the phenomena of alternating generations (in their widest sense) into two main groups according to their origin, designating the cases of one group as true metagenesis and those of the other as heterogenesis.38 Metagenesis takes its origin from a phyletic series of dissimilar forms, whilst heterogenesis originates from a phyletic series of similar forms—this series, so far as we can at present judge, always consisting of similar sexual generations. The former would thus nearly coincide with Haeckel’s progressive, and the latter with his retrogressive metagenesis. Metagenesis may further originate in various ways. In the first place, from metamorphosis, as for example, in the propagation of the celebrated Cecidomyia with nursing larvæ. The power which these larvæ possess of propagating themselves asexually has evidently been acquired as a secondary character, as appears from the fact that there are many species of the same genus the larvæ of which do not nurse, these larvæ being themselves undoubted secondary forms produced by the adaptation of this stage of phyletic development to a mode of life widely different from that of the later stages. In the form now possessed by these larvæ they could never have represented the final stage of their ontogeny, neither could they have formerly possessed the power of sexual propagation. The conclusion seems inevitable that metagenesis has here proceeded from metamorphosis; that is to say, one stage of the ontogeny, by acquiring asexual propagation, has changed the originally existing metamorphosis into metagenesis.

Lubbock39 is undoubtedly correct when, for cases like that just mentioned, he attempts to derive alternation of generations from metamorphosis. But if we exclude heterogenesis there still remain a large number of cases of true metagenesis which cannot be explained from this point of view.

It must be admitted, with Haeckel, that the alternation of generations in the Hydromedusæ and Trematoda does not depend, as in the case of Cecidomyia, upon the larvæ having acquired the power of nursing, but that the inferior stages of these species always possessed this power which they now only preserve. The nursing Trematode larvæ now existing may possibly have been formerly able to propagate themselves also sexually, this mode of propagation having at the present time been transferred to a later phyletic stage. In this case, therefore, metagenesis was not properly produced by metamorphosis, but arose therefrom in the course of the phyletic development, the earlier phyletic stages abandoning the power of sexual reproduction, and preserving the asexual mode of propagation. A third way in which metagenesis might originate is through polymorphosis. When the latter is combined with asexual reproduction, as is especially the case with the Hydrozoa, metagenesis may be derived therefrom. The successive stages of transformation of one and the same physiological individual do not in these cases serve as the point of departure for alternation of generation, but the different contemporary forms living gregariously into which the species has become divided through functional differentiation of the various individuals of the same stock. Individuals are here produced which alone acquire the power of sexual reproduction, and metagenesis is thus brought about, these individuals detaching themselves from the stock on which they originated, while the rest of the individuals remain in combination, and retain the asexual mode of propagation. No sharp distinction can be otherwise drawn between this and the cases previously considered.40 The difference consists only in the whole cycle of reproduction being performed by one stock; both classes have the common character that the different phyletic stages never appear in the same individual (metamorphosis), but in the course of further phyletic development metagenesis at the same time arises, i.e. the division of these stages among a succession of individuals. We are therefore able to distinguish this primary metagenesis from the secondary metagenesis arising from metamorphosis.

It is not here my intention to enter into the ultimate causes of metagenesis; in this subject we should only be able to advance by making vague hypotheses. The phenomenon of seasonal dimorphism, with which this work has mainly to deal, is evidently far removed from metagenesis, and it was to make this clear that the foregoing observations were brought forward. The characters common in the origin of metagenesis are to be found, according to the views previously set forth, in the facts that here the faculty of asexual and of sexual reproduction is always distributed among several phyletic stages of development which succeed each other in an ascending series (progressive metagenesis of Haeckel), whereas I find differences only in the fact that the power of asexual propagation may (in metagenesis) be either newly acquired (larva of Cecidomyia) or preserved from previous ages (Hydroida). It seems that in this process sexual reproduction is without exception lost by the earlier, and remains confined solely to the most recent stages.

From the investigations on seasonal dimorphism it appears that a cycle of generations can arise in an entirely different way. In this case a series of generations originally alike are made dissimilar by external influences. This appears to me of the greatest importance, since seasonal dimorphism is without doubt closely related to that mode of reproduction which has hitherto been exclusively designated as heterogenesis, and a knowledge of its mode of origination must therefore throw light on the nature and origin of heterogenesis in general.

In seasonal dimorphism, as I have attempted to show, it is the direct action of climate, and indeed chiefly that of temperature, which brings about the change in some of the generations. Since these generations have been exposed to the alternating influence of the summer and winter temperature a periodical dimorphism has been developed—a regular cycle of dissimilar generations. It has already been asserted that the consecutive generations of a species comport themselves with respect to heredity in a manner precisely similar to that of the ontogenetic stages, and at the same time such succeeding generations point out the parallelism between metamorphosis and heterogenesis. If influences capable of directly or indirectly producing changes operate on any particular stage of development, these changes are always transmitted to the same stage. Upon this metamorphosis depends. In a precisely similar manner changes which operated periodically on certain generations (1, 3, 5, for instance) are transmitted to these generations only, and not to the intermediate ones. Upon this depends heterogenesis. We have just been led to the comprehension of heterogenesis by cyclical heredity, by the fact that a cycle is produced whenever a series of generations exists under regularly alternating influences. In this cycle newly acquired changes, however minute in character at first, are only transmitted to a later, and not to the succeeding generation, appearing only in the one corresponding, i.e. in that generation which exists under similar transforming influences. Nothing can more clearly show the extreme importance which the conditions of life must have upon the formation and further development of species than this fact. At the same time nothing shows better that the action of these conditions is not suddenly and violently exerted, but that it rather takes place by small and slow operations. In these cases the long-continued accumulation of imperceptibly small variations proves to be the magic means by which the forms of the organic world are so powerfully moulded. By the application of even the greatest warmth nobody would be able to change the winter form of A. Levana into the summer form; nevertheless, the summer warmth, acting regularly on the second and third generations of the year, has, in the course of a lengthened period, stamped these two generations with a new form without the first generation being thereby changed. In the same region two different climatic varieties have been produced (just as in the majority of cases climatic varieties occur only in separate regions) which alternate with each other, and thus give rise to a cycle of which each generation propagates itself sexually.

But even if seasonal dimorphism is to be ascribed to heterogenesis, it must by no means be asserted that those cases of cyclical propagation hitherto designated as heterogenesis are completely identical with seasonal dimorphism. Their identity extends only to their origin and manner of development, but not to the mode of operation of the causes which bring about their transformation. Both phenomena have a common mode of origination, arising from similar (monomorphic) sexual generations and course of development, a cycle of generations with gradually diverging characters coming into existence by the action of alternating influences. On the other hand, the nature of the changes by which the secondary differs from the primary generation may be referred to another mode of action of the exciting causes. In seasonal dimorphism the differences between the two generations are much less than in other cases of heterogenesis. These differences are both quantitatively less, and are likewise qualitative, affecting only characters of biological insignificance.41 The variations in question are mostly restricted to the marking and colouring of the wings and body, occasionally affecting also the form of the wing, and in a few cases the size of the body (Plebeius Amyntas), whilst the bodily structure—so far at least as my investigations extend—appears to be the same in both generations.42

The state of affairs is quite different in the remaining cases of heterogenesis; here the entire structure of the body appears to be more or less changed, and its size is often very different, nearly all the internal organs differing in the two generations. According to Claus,43 “we can scarcely find any other explanation of the mode of origination of heterogenesis than the gradual and slow advantageous adaptation of the organization to important varying conditions of life”—a judgment in which this author is certainly correct. In all such cases the change does not affect unimportant characters, as it does in butterflies, but parts of biological or physiological value; and we cannot, therefore, consider such changes to have originated through the direct action of altered conditions of life, but indirectly through natural selection or adaptation.

Thus, the difference between seasonal dimorphism and the other known cases of heterogenesis consists in the secondary form in which the species appears in the former originating through the direct action of external conditions, whilst in the latter this form most probably originates through the indirect action of such influences. The first half of the foregoing proposition is alone capable of provisional proof, but it is in the highest degree probable that the latter half is also correct. Naturally we cannot say to what extent the direct action of external conditions plays also a part in true heterogenesis, as there have been as yet no experiments made on its origin. That direct action, working to a certain extent co-operatively, plays only a secondary part, while the chief cause of the change is to be found in adaptation, no one can doubt who keeps in view, for instance, the mode of propagation discovered by Leuckart in Ascaris nigrovenosa. In this worm, the one generation lives free in the water, and the other generation inhabits the lungs of frogs, the two generations differing from one another in size of body and structure of internal organs to an extent only possible with the true Nematoda.

To prevent possible misunderstanding, let it be finally noted—even if superfluous—that the changes causing the diversity of the two generations in seasonal dimorphism and heterogenesis are not of such a nature that the value of different “specific characters” can be attached to them. Distinctly defined specific characters are well known not to occur generally, and it would therefore be erroneous to attach but little value to the differences in seasonal dimorphism because these chiefly consist in the colouring and marking of the wings. The question here under consideration is not whether two animal forms have the value of species or of mere varieties—a question which can never be decided, since the reply always depends upon individual opinion of the value of the distinctions in question, and the idea of both species and varieties is moreover purely conventional. The question is, rather, whether the distinguishing characters possess an equal constancy—that is, whether they are transmitted with the same force and accuracy to all individuals; and whether they occur, therefore, in such a manner that they can be practically employed as specific characters. With respect to this, it cannot be doubtful for a moment that the colouring and marking of a butterfly possess exactly the same value as the constant characters in any other group of animals, such as the palate-folds in mice, the structure of the teeth in mammals, the number and form of the wing and tail feathers in birds, &c. We have but to remember with what wonderful constancy often the most minute details of marking are transmitted in butterflies. The systematist frequently distinguishes between two nearly allied species, as for instance in the Lycænidæ, chiefly by the position of certain insignificant black spots on the under side of the wing (P. Alexis female, and P. Agestis); and this diagnosis proves sufficient, since P. Alexis, which has the spots in a straight row, has a different caterpillar to P. Agestis, in which the central spot is nearer the base of the hind wing!

For the reasons just given, I maintain that it is neither justifiable nor useful to designate the di- and polymorphism of butterflies as di- and polychroism, and thereby to attribute but little importance to these phenomena.44 This designation would be only justifiable if the differences of colour were due to other causes than the differences of form, using this last word in a narrow sense. But it has been shown that the same direct action of climate which originates new colours, produces also in some species differences of form (contour of wing, size, &c.); whilst, on the other hand, it has long been known that many protective colours can only be explained by the indirect action of external conditions.

When I raise a distinction in the nature of the changes between seasonal dimorphism and the remaining known cases of heterogenesis, this must be taken as referring only to the biological or physiological result of the change in the transformed organism itself. In seasonal dimorphism only insignificant characters become prominently changed, characters which are without importance for the welfare of the species; while in true heterogenesis we are compelled to admit that useful changes, or adaptations, have occurred.

Heterogenesis may thus be defined either in accordance with my proposal or in the manner hitherto adopted, since it may be regarded as more morphological than the cyclical succession of differently formed sexual generations; or, with Claus, as the succession of different sexual generations, “living under different conditions of existence”—a definition which applies in all cases to seasonal dimorphism. Varying conditions of existence, in their widest sense, are the result of the action of different climates; and a case has been made known recently in which it is extremely probable that the climatic differences of the seasons have produced a cycle of generations by influencing the processes of nutrition. This case is quite analogous to that which we have observed in the seasonal dimorphism of butterflies, but with the distinction that the difference between the winter and summer generations does not, at least entirely, consist in the form of the reproductive adult, but almost entirely in its ontogeny—in the mode of its development. A comparison of this case with the analogous phenomenon in butterflies, may be of interest. In the remarkable fresh-water Daphnid, Leptodora hyalina Lillejeborg, it was proved some years ago by P. E. Müller,45 who studied the ontogeny, that this last was direct, since the embryo, before leaving the egg, already possesses the form, members, and internal organs of the adult. This was, at least, the case with the summer eggs. It was subsequently shown by Sars46 that this mode of development only holds good for the summer brood, the winter eggs producing an embryo in the spring which possesses only the three first pairs of limbs, and, instead of compound eyes, only a single frontal eye, thus exhibiting briefly, at first, the structure of a Nauplius, and gradually acquiring that of Leptodora. The mature form derived from the winter eggs is not distinguishable from the later generations, except by the presence of the simple larval eye, which appears as a small black spot. The generations when fully developed are thus distinguished only by this minute marking, but the summer generation undergoes direct development, whilst the winter generation, on the contrary, is only developed by metamorphosis, beginning with the simplest Crustacean type, and thus fairly representing the phyletic development of the species. We therefore see, in this case, the combination of a metamorphic and a direct development taking place to a certain extent under our eyes. It cannot be proved with certainty what the cause of this phenomenon may be, but the conjecture is almost unavoidable that it is closely related to the origin of the seasonal dimorphism of butterflies, since both depend on the alternating climatic influences of summer and winter: it is most probable that these influences have directly47 brought about a shortening of the period of development in summer. Thus we have here a case of heterogenesis nearly related to the seasonal dimorphism of butterflies in a twofold manner—first, because the cycle of generations is also in this case brought about by the direct action of the external conditions of life; and secondly, the winter form is here also the primary, and the summer form the secondary one.

In accordance with the idea first introduced into science by Rudolph Leuckart, we have hitherto understood heterogenesis to be only the alternation of dissimilar sexual generations. From this point of view the reproduction of Leptodora can be as little ascribed to heterogenesis as can that of Aphis or Daphnia, although the apparent agamic reproduction of the winter and a portion of the summer generation is undoubtedly parthenogenesis and not propagation by nursing.48 As has already been said, however, I would attribute no fundamental importance to the criterion of agamic reproduction—the more especially because we are ignorant of the physiological significance of the two modes of propagation; and further, because this principle of classification is entirely external, and only valuable in so far as no better one can be substituted for it. A separation of the modes of cyclical propagation according to their genesis appears to me—especially if practicable—not alone to be of greater value, but the only correct one, and for this the knowledge of the origin of seasonal dimorphism seems to me to furnish a possible method.

If, as was indicated above, we designate as metagenesis (in the narrow sense) all those cases in which it must be admitted that a series of differently aged phyletic stages have furnished the points of departure, and as heterogenesis those cases in which similar phyletic stages have been compelled to produce a cycle of generations by the periodic action of external influences, it is clear that the scope of heterogenesis is by this means considerably extended, and at the same time sharply and precisely defined.

Under heterogenesis then is comprised, not only as heretofore the reproduction of Ascaris nigrovenosa, of Leptodora appendiculata, and of the cattle-lice, but also that of the Aphides, Coccidæ, Daphniidæ, Rotatoria, and Phyllopoda, and, in short, all those cases in which we can determine the former identity of the two kinds of generations from their form, anatomical structure, and mode of reproduction. This conclusion is essentially supported by a comparison of the most closely allied species. Thus, for instance, when we see the genus Aphis and its allies related on all sides to insects which propagate sexually in all generations, and when we further observe the great similarity of the whole external and internal structure in the two kinds of generations of Aphis, we are forced to the conjecture that the apparent asexual reproduction of the Aphidæ is in reality parthenogenesis, i.e., that it has been developed from sexual reproduction. Neither can it be any longer disputed that in this case, as well as in that of Leptodora and other Daphniidæ, the same female alternately propagates parthenogenetically, and produces eggs requiring fertilization. This was established by Von Heyden49 some years ago, in the case of Lachnus Querci, and has been since confirmed by Balbiani.50

There can be no doubt that in all these cases the cycle of generations has been developed from phyletically similar generations. But instances are certainly conceivable which present themselves with less clearness and simplicity. In the first place, we do not know whether parthenogenesis may not finally settle down into complete asexual reproduction. Should this be the case, it might be possible that from heterogenesis a mode of propagation would ultimately arise, which was apparently indistinguishable from pure metagenesis. Such a state of affairs might result, if the generations settling into asexual reproduction (as, for instance, the plant-lice), at the same time by adaptation to varying conditions of life, underwent considerable change of structure, and entered upon a metamorphosis to some extent retrogressive. We should then be inclined to regard these generations as an earlier phyletic stage, whilst, in fact, they would be a later one, and the idea of metagenesis would thus have been formed after the manner of heterogenesis.

On the other hand, it is equally conceivable that heterogenesis may have been developed from true metagenesis in the case of larvæ which, having acquired the faculty of asexual propagation, are similar in function to sexually mature insects. This possibility is not at first sight apparent. If the nursing-larvæ of the Cecidomyiæ were as much like the sexual insects as are the young Orthoptera to the sexually mature forms, we should not know whether to regard them as degraded sexual insects, or as true larvæ which had attained the power of asexual propagation. Their propagation would be considered to be parthenogenesis; and as it could not be denied that heterogenesis was here manifest, the mode of development of their particular kind of propagation might be proved, i.e., it might be demonstrated, that the generations now parthenogenetic were formerly mere reproductive larval stages.

I have only offered these last observations in order to show on what uncertain ground we are still standing with regard to this subject whenever we deal with the meaning of any particular case, and how much still remains to be done. It appears certain that the two forms of cyclical propagation, heterogenesis and metagenesis, originate in entirely distinct ways, so that it must be admitted that, under these circumstances, the idea of the existing conditions respecting the true genesis may possibly be erroneous. To indicate the manner in which the cyclical mode of propagation has arisen in any single case, would only be possible by a searching proof and complete knowledge of existing facts in addition to experiments.

VI. General Conclusions.

I shall not here give a repetition and summary of the results arrived at with respect to seasonal dimorphism, but rather the general conclusions derived from these results; and, at the same time, I may take the opportunity of raising certain questions which have not hitherto found expression, or have been but briefly and casually stated.

It must, in the first place, be admitted that differences of specific value can originate through the direct action of external conditions of life only. Of the truth of this proposition there can be no doubt, after what has been above stated concerning the difference between the two forms of any seasonally dimorphic species. The best proof is furnished by the older systematists, to whom the genetic relationship of the two forms was unknown, and who, with unprejudiced taxonomy, in many cases indicated their distinctness by separate specific names. This was the case with Araschnia Levana and Prorsa, Euchloe Belia and Ausonia, E. Belemia and Glauce, Plebeius Polysperchon and Amyntas. In the presence of these facts it can scarcely be doubted that new species can be formed in the manner indicated; and I believe that this was and is still the case, with butterflies at least, to a considerable extent; the more so with these insects, because the striking colours and markings of the wings and body, being in most cases without biological significance, are useless for the preservation of the individual or the species, and cannot, therefore, be objects of natural selection.

Darwin must have obtained a clear insight into this, when he attempted to attribute the markings of butterflies to sexual and not to natural selection. According to this view, every new colour or marking first appears in one sex accidentally,51 and is there fixed by being preferred by the other sex to the older coloration. When the new ornamentation becomes constant (in the male for example), Darwin supposes that it becomes transferred to the female by inheritance, either partially or completely, or not at all; so that the species, therefore, remains more or less sexually dimorphic, or (by complete transference) becomes again sexually monomorphic.

The admissibility of such different, and, to a certain extent, arbitrarily limited inheritance, has already been acknowledged. The question here concerned is, whether Darwin is correct when he in this manner attributes the entire coloration of butterflies to sexual selection. The origin of seasonal dimorphism appears to me to be against this view, howsoever seductive and grand the latter may seem. If differences as important as those which exist between the summer and winter forms of many butterflies can be called forth by the direct action of a changed climate, it would be extremely hazardous to attribute great importance to sexual selection in this particular case.

The principle of sexual selection appears to me to be incontestible, and I will not deny that it is also effective in the case of butterflies; but I believe that as a final explanation of colour this agency can be dispensed with, inasmuch as we see that considerable changes of colour can occur without the influence of sexual selection.52

The question now arises, how far does the transforming influence of climate extend? When a species has become transformed by climatic change to such an extent that its new form possesses the systematic value of a new species, does it return to its older form by removal to the old climatic conditions? or would it under these circumstances become again transformed in a new manner? This question is not without importance, inasmuch as in the first case climatic influences would be of little value in the formation of species, and there would result at most only a fluctuation between two extremes. In the same manner as in seasonally dimorphic species the summer and winter forms now alternate with each other every year, so would the forms produced by warmth and cold then alternate in the greater periods of the earth’s history. Other groups of animals are certainly changed by the action of different climatic influences; but in butterflies, as I believe I have proved, temperature plays the chief part, and as this only oscillates between rather narrow limits, it admits of no great differences of coloration.

The question thus suggests itself, whether species of butterflies only oscillate between two forms, or whether climatic change, when sufficiently great to produce variation, does not again originate a new form. Inasmuch as the reversion experiments with seasonally dimorphic butterflies appear to correspond with the latter view, I believe that this must be admitted. I am of opinion that an old form never again arises through change of climate, but always a new one; so that a periodically recurring change of climate is alone sufficient, in the course of a long period of time, to admit of new species arising from one another. This, at least, may be the case with butterflies.

My views rest essentially upon theoretical considerations. It has already been insisted upon, as results immediately from the experiments, that temperature does not act on the physical constitution of the individual in the same manner as acid or alkali upon litmus paper, i.e., that one and the same individual does not produce this or that coloration and marking according as it is exposed to warmth or cold; but rather that climate, when it influences in a similar manner many succeeding generations, gradually produces such a change in the physical constitution of the species that this manifests itself by other colours and markings. Now when this newly acquired physical constitution, established, as we may admit, throughout a long series of generations, is again submitted to a constant change of climate, this influence, even if precisely similar to that which obtained during the period of the first form of the species, cannot possibly reproduce this first form. The nature of the external conditions may be the same, but not so the physical constitution of the species. Just in the same manner as a Pieris (as has been already shown), a Lycæna, or a Satyrus, produces quite different varieties under the transforming influence of the same climate, so must the variation originating from the transformed species of our present case after the beginning of the primary climate be different from that primary form of the species, although perhaps in a less degree. In other words, if only two different climates alternated with each other during the earth’s geological periods, every species of butterfly submitted to these changes of climate would give rise to an endless series of different specific forms. The difference of climate would in reality be greater than supposed, and for any given species the climatic variation would not only occur through the periodic shifting of the ecliptic, but also through geological changes and the migrations of the species itself, so that a continuous change of species must have gone on from this sole cause of alternation of climate. When we consider that many species elsewhere extinct have become locally preserved, and when, further, to these we add those local forms which have arisen by the prevention of crossing (amixia), and finally take into consideration the important effects of sexual selection, we can no longer be astonished at the vast numbers of species of butterflies which we now meet with on the earth.

Should any one be inclined to conclude, from my reversion experiments with seasonally dimorphic butterflies, that the secondary species when exposed to the same climate as that which produced it must revert to the primary, he forgets that this reversion to the winter form is nothing but a reversion—i.e., a sudden return to a primary form through peculiar laws of inheritance—and by no means a gradual re-acquisition of this primary form under the gradual influence of the primary climate. Reversion to the winter form occurs also through other influences, as, for instance, by high temperature. Reversions of this kind, depending on laws of heredity, certainly happen with those cases of transmutation which do not alternate with the primary form, as in seasonal dimorphism, but which occur continuously. They would, however probably be more quickly suppressed in such cases than in seasonal dimorphism, where the constant alternation of the primary and secondary forms must always maintain the tendency of the latter to produce the former.

That the above conclusion is correct—that a secondary species, when exposed to the external conditions under the influence of which the primary form originated, does not again revert to the latter—is proved by experience with plants. Botanists53 assure us “that cultivated races which become wild, and are thus brought back to their former conditions of life, do not become changed into the original wild form, but into some new one.”

A second point which appears to me to be elucidated by seasonal dimorphism, is the origin of variability. It has already been prominently shown that secondary forms are for the most part considerably more variable than primary forms. From this it follows that similar external influences either induce different changes in the different individuals of a species, or else change all individuals in the same manner, variability arising only from the unequal time in which the individuals are exposed to the external influence. The latter is undoubtedly the case, as appears from the differences which are shown by the various individuals of a secondary form. These are always only differences of degree and not of kind, as is perhaps most distinctly shown by the very variable A. Prorsa (summer form), in which all the occurring variations differ only by the Levana marking being more or less absent, and, at the same time, by approximating more or less to the pure Prorsa marking; but changes in a totally different direction never occur. It is likewise further evident, as has been mentioned above, that allied species and genera, and even entire families (Pieridæ), are changed by similar external inducing causes in the same manner—or, better, in the same direction.

In accordance with these facts the law may be stated, that, in butterflies at least, all the individuals of a species respond to the same external influences by similar changes, and that, consequently, the changes brought about by climatic influences take a fixed direction, determined by the physical constitution of the species. When, however, new climatic forms of butterflies, in which natural selection is completely excluded, and the nature of the species itself definitely determines the direction of the changes, nevertheless show variability from the very beginning, we may venture to conclude that every transformation of a species generally begins with a fluctuation of its characters. But when we find the primary forms of butterflies always far more constant, this shows that the continued crossing of the individuals of a species to a certain extent balances the fluctuations of form. Both facts taken together confirm the law formerly enunciated by me,54 that in every species a period of variability alternates with one of (relative) constancy—the latter indicating the culmination, and the former the beginning or end, of its development. I here call to mind this law, because the facts which I advanced at that time, viz., Hilgendorf’s history of the phyletic development of the Steinheim fossil shells, having since become somewhat doubtful, one might easily be inclined to go too far in mistrusting them and refuse to give them any weight at all.55

In the essay just indicated I traced the origin of a certain class of local forms to local isolation. I attempted to show that when a species finds itself in an isolated district in a condition (period) of variability, it must there necessarily acquire somewhat deviating characters by being prevented from crossing with the individuals of other regions, or, what comes to the same thing, a local form must originate. This production of local forms results because the different variations which, for the time being, constitute the variability of the species, would always be in a different numerical proportion in the isolated district as compared with other regions; and further, because constancy is produced by the crossing of these (isolated) varieties among themselves; so that the resultant of the various components is (local) variation. If the components are dissimilar the resultant would also be different, and thus, from a theoretical point of view, there seems to me no obstacle in the way of the production of such local forms by the process of ‘amixia.’ I believe that I have further shown that numerous local forms can be conceived to have arisen through this process of preventive crossing, whilst they cannot be explained by the action of climatic influences.

That I do not deny the existence of true climatic forms in admitting this principle of ‘amixia,’ as has been frequently imagined, appears sufficiently from the treatise in question. The question arises, however, whether climatic influences may not also originate forms by ‘amixia’ by making a species variable. It would be difficult at present to decide finally upon this subject. If, however, in all cases a variation in a certain fixed direction occurred through climatic influences, a form could not arise by ‘amixia’ from such a variability, since the components could then produce resultants different only in degree and not in kind. But we are not yet able to extend our researches to such fine distinctions.

As a final, and not unimportant result of these investigations, I may once more insist that dissimilar influences, when they alternatingly affect a long series of originally similar generations in regularly recurring change, only modify the generations concerned, and not intermediate ones. Or, more briefly, cyclically acting causes of change produce cyclically recurring changes: under their influence series of monomorphic generations become formed into a cycle of di- or polymorphic generations.

There is no occasion to return here to the immediate evidence and proof of the foregoing law. In the latter, however, is comprised the question—is not the cycle of generations produced by cyclical heredity ultimately equivalent to Darwin and Haeckel’s homochronic heredity which forms the ontogenetic stages into a cycle? It is possible that from this point, in the future, the nature of the processes of heredity, which are still so obscure, may be penetrated into, and both phenomena traced to the same cause, as can now be only surmised but not clearly perceived.

Finally, the most general, and in so far chief result of these investigations, appears to me to lie in the conclusion, which may be thus formulated:—A species is only caused to change through the influence of changing external conditions of life, this change being in a fixed direction which entirely depends on the physical nature of the varying organism, and is different in different species, or even in the two sexes of the same species.

I am so little disposed to speak in favour of an unknown transforming power that I may here again insist that the transformation of a species only partly depends upon external influences, and partly on the specific constitution of the particular form. I designate this constitution ‘specific,’ inasmuch as it responds to the same inciting cause in a manner different to the constitution of another species. We can generally form a clear conception why this should be the case; for not only is there in another species a different kind of latent vital activity, but each species has also a different developmental history. It must be admitted that, from the earliest period of the formation of an organism, and throughout all its intermediate stages, properties which have become established, such as growth, nutrition, or tendency to development, have been transferred to the species now existing, each of which bears these tendencies in itself to a certain extent. It is these innate tendencies which determine the external and internal appearance of the species at every period of its life, and which, by their reaction to external factors, represent the life of the individual as well as that of the species. Since the sum of these inherited tendencies must vary more or less in every species, not only is the different external appearance of species as well as their physiological and biological diversity thus explained, but it necessarily follows therefrom, that different species must respond differently to those external causes which tend to produce a change in their form.

Now, this last conclusion is equivalent to the statement that every species, through its physical constitution, (in the sense defined) is impressed with certain fixed powers of variation, which are evidently extraordinarily numerous in the case of each species, but are not unlimited; they permit of a wide range for the action of natural selection, but they also limit its functions, since they certainly restrain the course of development, however wide the latter may be. I have elsewhere previously insisted56 that too little is ascribed to the part played by the physical constitution of species in the history of their transformation, when the course of this transformation is attributed entirely to external conditions. Darwin certainly admits the importance of this factor, but only so far as it concerns the individual variation, the nature of which appears to him to depend on the physical constitution of the species. I believe, however, that in this directive influence lies the precise reason why, under the most favourable external circumstances, a bird can never become transformed into a mammal—or, to express myself generally, why, from a given starting-point, the development of a particular species cannot now attain, even under the most favourable external conditions, any desired goal; and why, from this starting-point, given courses of development, even when of considerable latitude, must be restricted, just as a ball rolling down a hill is diverted by a fixed obstacle in a direction determined by the position of the latter, and depending on the direction of motion and the velocity at the moment of being diverted.

In this sense I agree with Askenasy’s “fixed” direction of variation; but not if another new physical force directing variation itself is thereby intended.57 The explanation of the phenomena does not appear to me to require such an admission, and, if unnecessary, it is certainly not legitimate. According to my view, transmutation by purely internal causes is not to be entertained. If we could absolutely suspend the changes of the external conditions of life, existing species would remain stationary. The action of external inciting causes, in the widest sense of the word, is alone able to produce modifications; and even the never-failing “individual variations,” together with the inherited dissimilarity of constitution, appear to me to depend upon unlike external influences, the inherited constitution itself being dissimilar because the individuals have been at all times exposed to somewhat varying external influences.

A change arising from purely internal causes seems to me above all quite untenable, because I cannot imagine how the same material substratum of physical constitution of a species can be transferred to the succeeding generation as two opposing tendencies. Yet this must be the case if the direction of development transferred by heredity is to be regarded as the ultimate ground both of the similarity and dissimilarity to the ancestors. All changes, from the least to the greatest, appear to me to depend ultimately only on external influences; they are the response of the organism to external inciting causes. It is evident that this response must be different when a physical constitution of a different nature is affected by the same inciting cause, and upon this, according to my view, depends the great importance of these constitutional differences.

If, under “heredity,” we comprise the totality of inheritance—that is to say, the physical constitution of a species at any time, and therefore the restricted and, in the foregoing sense, pre-determined power of variation, whilst under “adaptation” we comprehend the direct and indirect response of this physical constitution to the changes in the conditions of life, I can agree with Haeckel’s mode of expression, and with him trace the transformation of species to the two factors of heredity and adaptation.

APPENDIX I. EXPERIMENTS.

Experiments with Araschnia Levana.

1. Bred from eggs laid by a female of the winter form on 12th-15th May, 1868, in a breeding-cage. The caterpillars emerged on 20th-22nd May, and pupated on 7th-9th June. The pupæ, kept at the ordinary temperature, produced:—

On the 19th of June 4 butterflies.

” 20th ” 5 ”

” 21st ” 10 ”

” 22nd ” 9 ”

” 23rd ” 7 ”

” 25th ” 13 ”

Total 48 ”

All these butterflies were of the Prorsa type, 3 females having a considerable amount of yellow, but none with so much as figs. 3, 4, 7, 8, or 9. Pl. I.

2. August 12th, 1868, found larvæ of the third generation, which pupated at the beginning of September, and were kept in a room not warmed. In September three butterflies emerged in the Prorsa form, the remainder hibernating and producing, after being placed in a heated room at the end of February, from the 1st to the 17th of March, 1869, more butterflies, all of the Levana form.

3. Larvæ found on the 17th June, 1869, were sorted according to colour; the yellow ones, with light brown spines, produced, at the ordinary temperature, on 8th-12th July, 13 butterflies, 12 of which showed the ordinary Prorsa type, and one, a male, possessing more yellow than fig. 3, Pl. I., must be considered as a Porima type.

4. From caterpillars of the second generation, found at the same time as those of Exp. 3, 30 pupæ were placed in the refrigerator (temperature 8°-10° R.) on June 25th. When the box was opened on August 3rd, almost all had emerged, many being dead, and all, without exception, were of the intermediate form (Porima), although nearer the Prorsa than the Levana type.

5. A large number of caterpillars of the second generation, found at the same time, pupated, and were kept at a high summer temperature. After a pupal period of about 19 days, some 70 butterflies emerged from 28th June to 5th July, all of the Prorsa form, with the exception of 5, which were strongly marked with yellow (Porima).

6. The 70 butterflies of the foregoing experiment were placed in an enclosure 6 feet high, and 8 feet long, in which, during warm weather, they freely swarmed on flowers. Copulation was only once observed, and but one female laid eggs on nettle on July 4th. At the high summer temperature prevailing at the time, these eggs produced butterflies after 30–31 days (third generation). All were Prorsa, with more or less yellow; among 18 none were completely Porima.

7. Young larvæ of the fourth generation, found on the 8th of August, were reared in a hothouse (17°-20° R.). They pupated on 21st-23rd August. Of these:—

A. 56 pupæ were placed on ice (0°-1° R.) for five weeks, and then allowed to hibernate in a room not warmed. In April, 1870, they all gave the Levana form, with the exception of a single Porima.

B. About an equal number of pupæ were placed in the hothouse, but without any result; for, notwithstanding a temperature of 12°-24° R., not a single butterfly emerged in the course of October and November. The pupæ were then allowed to hibernate in an unheated room, and in April and May gave nothing but Levana.

8. Caterpillars of the second generation, found at the beginning of June, 1870, pupated on 13th-15th June, and gave, at the ordinary temperature, on June 29th-30th, 7 butterflies of the Prorsa form.

9. Pupæ of the same (second) generation were placed immediately after pupation on June 18th, 1870, in a refrigerator (0°-1° R.), and after remaining there four weeks (till July 18th) gave, at the ordinary summer temperature:—

On the 22nd of July, 2 Prorsa.

” 23rd ” 3 ”

” 24th ” 6 Porima, 4 of which were very similar to Levana.

” 25th ” 1 Levana, without the blue marginal line.

” 26th ” 2 Levana, also without the blue marginal line.

” 2nd August, 6 Porima.

Total 20

Of these 20 butterflies only 5 were of the pure Prorsa form.

10. Full grown larvæ of the fourth generation, found on August 20th, 1870, pupated on August 26th to September 5th. The pupæ were divided into three portions:—

A. Placed in the hothouse (12°-25° R.), immediately after pupation and left there till October 20th. Of about 40 pupæ only 4 emerged, 3 of which were Prorsa and 1 Porima. The remaining pupæ hibernated and all changed into Levana the following spring.

B. Kept in a room heated to 6°-15° R. from November. Not a single specimen emerged the same year. This lot of pupæ were added to C from November.

C. Placed on ice for a month immediately after pupation; then, from September 28th to October 19th in the hothouse, where no more butterflies emerged. The pupæ hibernated, together with those from lot B, in a room heated by water to 6°-15° R., and gave:—

On the 6th of February, 1 female Levana.

” 22nd ” 1 male Levana.

” 23rd ” 1 male Levana.

” 24th ” 1 female Levana.

” 25th ” 1 male and 1 female Levana.

” 28th ” 1 male and 1 female Levana.

” 1st of March, 1 male Levana.

” 13th ” 1 female Levana.

” 15th ” 1 female Levana.

” 19th ” 1 male Levana.

” 2nd of April, 2 male and 1 female Levana.

” 7th ” 1 female Levana.

” 21st ” 1 female Levana.

” 2nd of May, 1 female Levana.

Total 18 Levana, 10 of which were females.

The exact record of the time of emergence is interesting, because it is thereby rendered apparent that different individuals respond more in different degrees to a higher than to the ordinary temperature. Whilst with many an acceleration of development of 1–2 months occurred, others emerged in April and May, i.e. at the time of their appearance in the natural state.

11. Reared the second generation from eggs of the first generation. Emerged from the eggs on June 6th, 1872, pupated on July 9th. The pupæ were placed on ice (0°-1° R.) from July 11th till September 11th, and then transferred to a hothouse, where all emerged:—

On the 19th of September, 3 male Prorsa, 1 male Porima.

” 21st ” 13 Porima (12 males, 1 female), 2 female Levana.

” 22nd ” 14 Porima (12 males, 2 females) and 1 female Levana.

” 23rd ” 10 female Levana, 3 male Porima.

” 24th ” 5 female Levana.

” 25th ” 1 female Levana.

” 27th ” 3 female Levana.

” 4th of October, 1 male Porima.

Total 57 butterflies (32 males and 25 females),

only 3 of which were Prorsa, 32 Porima, and 22 Levana.

It must be pointed out, however, that among those specimens marked as “Levana” there were none which entirely corresponded with the natural Levana, or which indeed approximated so nearly to this form as did some of the specimens in Exp. 9. All were larger than the natural Levana, and possessed, notwithstanding the large amount of yellow, more black than any true Levana. In all artificially bred Levana the black band of the basal half of the hind wings is always interrupted with yellow, which is seldom the case with true Levana. The whole appearance of the artificial Levana is also coarser, and the contour of the wings somewhat different, the fore-wings being broader and less pointed. (See figs. 7 to 9, Pl. I.).

12. Larvæ of the fourth generation, found on September 22nd, 1872, were divided into two portions:—

A. Placed for pupation in an orchid-house at 12°-25° R., and allowed to remain there till December. In spite of the high temperature not a single butterfly emerged during this time, whilst pupæ of Vanessa C-album and Pyrameis Atalanta, found at the same time, and placed in the same hothouse, emerged in the middle of October. From the middle of December the pupæ were kept in an unheated room, and they emerged very late in the spring of 1873, all as Levana:—

On the 6th of June, 7 Levana.

” 8th ” 2 ”

” 11th ” 2 ”

” 12th ” 1 ”

” 15th ” 6 ”

” 16th ” 1 ”

” 19th ” 2 ”

Total 21 ”

B. Kept in an unheated room during the winter. The butterflies emerged from the 28th of May, all as Levana.

Experiments with Pierinæ.

13. Females of Pieris Rapæ, captured in April, laid eggs on Sisymbrium Alliaria. From these caterpillars were obtained, which pupated on 1st-3rd June. The pupæ were placed on ice from June 3rd till September 11th (0°-1° R.), and from September 11th till October 3rd in the hothouse (12°-24° R.), where there emerged:—

On the 23rd of October, 1 female.

” 24th ” 1 female.

” 25th ” 2 males, 1 female.

” 26th ” 1 female.

” 28th ” 1 male, 1 female.

Total 3 males, 5 females.

All these were sharply impressed with the characters of the winter form, the females all strongly yellow on the upper side, the males pure white; on the under side a strong black dusting on the hind wings, particularly on the discoidal cell. One pupa did not emerge in the hothouse, but hibernated, and gave in a heated room on January 20th, 1873, a female, also of the winter form.

14. Females of Pieris Napi, captured on 27th-28th April, 1872, laid eggs on Sisymbrium Alliaria. The larvæ bred from these pupated on May 28th to June 7th. The pupæ, shortly after transformation, were placed on ice, where they remained till Sept. 11th (three months). Transferred to the hothouse on October 3rd, they produced, up to October 20th, 60 butterflies, all with the sharply-defined characters of the winter form. The remaining pupæ hibernated in a room, and produced:—

On the 28th of April, 3 males, 6 females.

” 4th of May, 1 female.

” 12th ” 4 males.

” 15th ” 1 male, 1 female.

” 16th ” 1 male.

” 18th ” 1 male, 1 female.

” 19th ” 1 female.

” 20th ” 2 males, 1 female.

” 23rd ” 2 males.

” 26th ” 1 male.

” 29th ” 1 female.

” 3rd of June, 3 females.

” 6th ” 1 female.

” 9th ” 1 female.

” 21st ” 1 female.

” 2nd of July, 1 female.

Total 15 males, 19 females.

15. Several butterflies from Exp. 14, which emerged in May, 1873, were placed in a capacious breeding-house, where they copulated and laid eggs on rape. The caterpillars fed on the living plants in the breeding-house, and after pupation were divided into two portions:—

A. Several pupæ, kept at the ordinary summer temperature, gave butterflies on July 2nd, having the characters of the summer form.

B. The remainder of the pupæ were placed on ice immediately after transformation, and remained over three months in the refrigerator (from July 1st till October 10th). Unfortunately most of them perished through the penetration of moisture into the box. Only 8 survived, 3 of which emerged on the 20th of October as the winter form; the others hibernated in an unheated room, and emerged at the beginning of June, 1874. All 5 were females, and all exhibited the characters of the winter form. Notwithstanding a pupal period of eleven months, they did not possess these characters to a greater extent than usual, and did not, therefore, approximate to the parent-form Bryoniæ.

16. On June 12th, 1871, specimens of Pieris Napi, var. Bryoniæ, were captured on a mountain in the neighbourhood of Oberstorf (Allgäuer Alpen), and placed in a breeding-house, where they flew freely about the flowers; but although copulation did not take place, several females laid eggs on the ordinary garden cabbage. From these caterpillars were hatched, which at all stages of growth were exactly like those of the ordinary form of Napi. They throve well until shortly before pupation, when a fungoid epidemic decimated them, so that from 300 caterpillars only about 40 living pupæ were obtained. These also completely resembled the ordinary form of Napi, and showed the same polymorphism, some being beautifully green, others (the majority) straw yellow, and others yellowish grey. Only one butterfly emerged the same summer, a male, which, by the black dusting of the veins on the margin of the wings (upper side), could be with certainty recognized as var. Bryoniæ. The remaining pupæ hibernated in a heated room, and gave, from the end of January to the beginning of June, 10 males and 5 females, all with the characters of the var. Bryoniæ. They emerged:—

On the 22nd of January, 1 male.

” 26th ” 1 male.

” 3rd of February, 1 male.

” 4th ” 1 male.

” 5th ” 1 male.

” 7th ” 1 female.

” 9th ” 1 male.

” 24th ” 1 male.

” 4th of March, 1 female.

” 11th ” 1 male, 1 female.

” 6th of April, 1 female.

” 17th ” 1 male.

” 11th of May, 1 female.

” 3rd of June, 1 male.

We here perceive that the tendency to accelerate development through the action of warmth is, in this case, also very different in different individuals. Of the 16 butterflies only 1 kept to the normal period of development from July 27th to June 3rd, fully ten months; all the others had this period abbreviated, 1 male to eleven days, 8 specimens to six months, 4 to seven months, 2 to eight months, and 1 to nine months.

APPENDIX II.

Experiments with Papilio Ajax.58

From eggs of var. Telamonides laid on the last of May larvæ were obtained, which gave on June 22nd-26th, 122 pupæ. These, as fast as formed, were placed on ice in the refrigerator in small tin boxes, and when all the larvæ had become transformed the pupæ were transferred to a cylindrical tin box (4 in. diam. and 6 in. high), and packed in layers between fine shavings. The tin box was set in a small wooden one, which was put directly on the ice and kept there till July 20th. From that date, by an unfortunate accident, the box, instead of being kept on the surface of the ice in an ice-house, as was intended, was placed on straw near the ice, so that the action of the cold was modified, the outside pupæ certainly experiencing its full effects, but the inside ones were probably at a somewhat higher temperature. The ice failed on August 20th, so that the pupæ had been subjected to an equable low temperature in the refrigerator for three to four weeks, and to a lesser degree of cold in the ice-house for five weeks, the temperature of the last place rising daily, as the ice had all thawed by August 20th. On opening the box it was found (probably owing to the cold not having been sufficiently severe) that the butterflies had commenced to emerge. Twenty-seven dead and crippled specimens were removed, together with several dead pupæ. One butterfly that had just emerged was taken out and placed in a box, and when its wings had fully expanded it was found to be a “Telamonides of the most pronounced type.” The experimenter then states:—“Early in the morning I made search for the dead and rejected butterflies, and recovered a few. It was not possible to examine them very closely from the wet and decayed condition they were in, but I was able to discover the broad crimson band which lies above the inner angle of the hind wings, and which is usually lined on its anterior side with white, and is characteristic of either Walshii or Telamonides, but is not found in Marcellus. And the tip only of the tail being white in Walshii, while both tip and sides are white in Telamonides, enabled me to identify the form as between these two. There certainly were no Walshii, but there seemed to be a single Marcellus, and excepting that all were Telamonides.”

The remaining pupæ were kept in a light room where 3 Telamonides emerged the following day, and by September 4th 14 specimens of the same variety had emerged, but no Marcellus or intermediate forms. From the 4th to the 20th of September a few more Telamonides appeared, but between the 4th and 15th of the month 12 out of 26 butterflies that had emerged were intermediate between Telamonides and Marcellus, some approximating to one form and some to the other form. The first pure Marcellus appeared on September 4th, and was followed by one specimen on the 6th, 8th, 13th and 15th respectively. From this last date to October 3rd, 6 out of 10 were Marcellus and 3 intermediate. On September 3rd, a specimen intermediate between Telamonides and Walshii emerged, “in which the tails were white tipped as in Walshii, but in size and other characters it was Telamonides, though the crimson band might have belonged to either form.” Butterflies continued to emerge daily up to September 20th, after which date single specimens appeared at intervals of from four to six days, the last emergence being on October 16th. Thus, from the time the box was removed from the ice-house, the total period of emerging was fifty-seven days, some specimens having emerged before the removal of the box. With specimens of P. Ajax which appear on the wing the first season the natural pupal period is about fourteen days, individuals rarely emerging after a period of four to six weeks.

Between August 20th and October 16th, the 50 following butterflies emerged:—

On the 20th of August, 1 male Telamonides.

” 21st ” 1 male and 2 female Telamonides.

” 22nd ” 1 female Telamonides.

” 24th ” 1 female Telamonides.

” 29th ” 1 male Telamonides.

” 31st ” 1 female Telamonides.

” 1st of September, 1 female Telamonides.

” 2nd ” 1 female Telamonides.

” 3rd ” 1 female intermediate between Telamonides and Walshii.

” ” ” 1 male Telamonides.

” 4th ” 4 males and 1 female Telamonides.

” ” ” 2 males, medium, nearest Telamonides.

” ” ” 2 males, medium, nearest Marcellus.

” ” ” 2 males, Marcellus.

” 5th ” 1 male and 1 female Telamonides.

” ” ” 1 male medium, nearest Telamonides.

” 6th ” 1 male Marcellus.

” 7th ” 1 male Telamonides.

” 8th ” 1 male Marcellus and 1 female Telamonides.

” 9th ” 1 male Marcellus and 1 female medium, nearest Marcellus.

” 13th ” 1 male medium, nearest Marcellus.

” ” ” 1 male medium, nearest Telamonides.

” ” ” 1 male Marcellus.

” 14th ” 1 male Marcellus and 1 female medium, nearest Marcellus.

” ” ” 1 male medium, nearest Telamonides.

” 15th ” 1 male Marcellus.

” 16th ” 1 female Marcellus and 1 male Telamonides.

” 18th ” 1 male medium, nearest Marcellus.

” 19th ” 1 female Marcellus.

” 20th ” 1 male Telamonides.

” 24th ” 1 male Marcellus.

” 30th ” 1 female Marcellus.

” 2nd of October, 1 female Marcellus.

” 3rd ” 1 female medium, nearest Telamonides.

” 8th ” 1 female medium, nearest Telamonides.

” 16th ” 1 female medium, nearest Telamonides.

Total.

Telamonides 22 12 males, 10 females.

Telamonides partly Walshii 1 1 female.

Medium, nearest Telamonides 8 5 males, 3 females.

Medium, nearest Marcellus 6 4 males, 2 females.

Marcellus 13 9 males, 4 females.

50 30 males, 20 females.

All these butterflies were very uniform in size, being about that of the ordinary Telamonides. The specimens of Telamonides especially were “strongly marked, the crimson band in a large proportion of them being as conspicuous as is usual in Walshii, and the blue lunules near the tail were remarkably large and bright coloured. Of the Marcellus, in addition to the somewhat reduced size, the tails were almost invariably shorter than usual and narrower, and instead of the characteristic single crimson spot, nearly all had two spots, often large. In all these particulars they approach Telamonides.”

Adding to the Telamonides which emerged after August 20th most of those specimens which were found dead in the box at that date, the total number of this form is thus brought up to nearly 50. Of the 122 pupæ with which Mr. Edwards started, 28 remained in a state fit for hibernation, several having died without emerging. Previous experiments had shown that 28 out of 122 pupæ is not an unreasonable number to hibernate, so that the author concludes that the butterflies which emerged the same season would have done so naturally, and the effect of the artificial cold was not “to precipitate the emerging of any which would have slept” till the following spring. Now under ordinary circumstances all the butterflies which emerged the same season would have been of the Marcellus form, so that the cold changed a large part of these into the form Telamonides, some (probably from those pupæ which experienced the lowest temperature) being completely changed, and others (from those pupæ which were only imperfectly subjected to the cold) being intermediate, i.e., only partly changed. It appears also that several pupæ experienced sufficient cold to retard their emergence and stunt their growth, but not enough to change their form, these being the 13 recorded specimens of Marcellus. Had the degree of cold been equal and constant, the reversion would probably have been more complete. The application of cold produced great confusion in the duration of the pupal period, the emergence, instead of taking place fourteen days after the withdrawal of the cold, as might have been expected from Dr. Weismann’s corresponding experiment with Pieris Napi (Appendix I. Exps. 13 and 14), having been extended over more than two months.

From the results of this experiment it must be concluded that Telamonides is the primary form of the species.

Additional Experiments with Papilio Ajax.

[Communicated by Mr. W. H. Edwards, November 18th, 1879.]

Exp. 1.—In 1877 chrysalides of P. Ajax and Grapta Interrogationis (the eggs laid by females of the form Fabricii) were experimented upon; but the results were not satisfactory, for the reason that the author having been absent from home most of the time while the pupæ were in the ice-box, on his return found the temperature above 5°-6° R. And so far as could be told, the ice had been put in irregularly, and there might have been intervals during which no ice at all was in the box. Six chrysalides of the Grapta so exposed produced unchanged Umbrosa, the co-form with Fabricii. But all chrysalides from the same lot of eggs, and not exposed to cold, also produced Umbrosa. Nothing was learnt, therefore, respecting this species.

But chrysalides of Ajax, exposed at same time, did give changed butterflies to some extent. From a lot of 8, placed in the box when under twelve hours from pupation, and left for twenty-four days, there came 5 males and 3 females. Of these was 1 Telamonides in markings and coloration, and all the rest were between Marcellus and Telamonides. Two other chrysalides on ice for twenty-three days gave Telamonides, but 3 more exposed twenty-six days, and all one hour old when put on ice, were unchanged, producing Marcellus.

During the same season 6 other Ajax chrysalides were placed in the box, and kept at about 0°-1° R. One was one hour old, and remained for five days; 1 was one hour old, and remained for two days and three-quarters; 3 at three hours old for eight days; and 1 (age omitted), six days. All these gave unchanged butterflies of the form Marcellus.

Exp. 2.—In May, 1878, many chrysalides were placed in the ice-box, being from eggs laid by Ajax, var. Walshii. The youngest were but ten to fifteen minutes from pupation, and were soft; others at intervals up to twenty-four hours (the chrysalis is hard at about twelve hours); after that, each day up to eight days after pupation. All were removed from the box on the same day, 28th May. The exposure was from nineteen to five days, those chrysalides which were put on ice latest having the shortest exposure. The author wished to determine if possible whether, in order to effect any change, it was necessary that cold should be applied immediately after pupation or if one or several days might intervene between pupation and refrigeration. Inasmuch as no colour begins to show itself in the pupæ till a few hours, or at most a day or two, before the butterfly emerges, it was thought possible that cold applied shortly before that time would be quite as effective as if applied earlier and especially very soon after pupation. The result was, that more than half of the chrysalides exposed before they had hardened died: 1 exposed at ten minutes, 2 at one hour, 1 at two hours, 2 at three hours after pupation. On the other hand 1 at fifteen minutes produced a butterfly, 1 at two hours, another at twelve hours. The temperature was from 0°-1° R. most of the time, but varied somewhat each day as the ice melted. The normal chrysalis period is from eleven to fourteen days, in case the butterfly emerges the same season, but very rarely an individual will emerge several weeks after pupation.

On the 14th day after taking the pupæ from the ice, 1 Telamonides emerged from a chrysalis which had been placed in the ice-box three days after pupation, and was on ice sixteen days.

On 19th day, 1 Telamonides emerged from a pupa put on the ice twelve hours after pupation, and kept there eleven days.

On 19th day, 1 Walshii emerged from a pupa two hours old, and on ice eleven days.

All the rest emerged Marcellus, unchanged, but at periods prolonged in a surprising way.

1 on 43rd day exposed 15 minutes after pupation.

” 46th ” 2 hours ”

” 53rd ” 24 hours ”

” 62nd ” 6 days ”

” 63rd ” 4 days ”

” 66th ” 7 days ”

” 77th ” 4 days ”

” 81st ” 12 hours ”

” 91st ” 5 days ”

” 96th ” 19 hours ”

Five chrysalides lived through the winter, and all gave Telamonides in the spring of 1879.

It appeared, therefore, that the only effect produced by cold in all chrysalides exposed more than three days after pupation was to retard the emergence of the butterfly. But even in some of these earliest exposed, and kept on the ice for full nineteen days, the only effect seemed to be to retard the butterfly.

Exp. 3.—In June, 1879, eggs of the form Marcellus were obtained, and in due time gave 104 chrysalides. Of these one-third were placed in the ice-box at from twelve to twenty-four hours after pupation, and were divided into 3 lots.

1st, 9 pupæ, kept on ice 14 days.

2nd, 12 ” ” 20 days.

3rd, 11 ” ” 25 days.

Temperature 0°-1° R. most of the time, but varying somewhat as the ice melted. (Both in 1878 and 1879 Mr. Edwards watched the box himself, and endeavoured to keep a low temperature.)

Of the 69 chrysalides not exposed to cold, 34 gave butterflies at from eleven to fourteen days after pupation, and 1 additional male emerged 11th August, or twenty-two days at least past the regular period of the species.

Of the iced chrysalides, from lot No. 1 emerged 4 females at eight days and a half to nine days and a half after removal from the ice, and 5 are now alive (Nov. 18) and will go over the winter.

From lot No. 2 emerged 1 male and 5 females at eight to nine days; another male came out at forty days; and 5 will hibernate.

From lot No. 3 emerged 4 females at nine to twelve days; another male came out at fifty-four days; and 6 were found to be dead.

In this experiment the author wished to see as exactly as possible—First, in what points changes would occur. Second, if there would be any change in the shape of the wings, as well as in markings or coloration—that is, whether the shape might remain as that of Marcellus, while the markings might be of Telamonides or Walshii; a summer form with winter markings. Third, to ascertain more closely than had yet been done what length of exposure was required to bring about a decided change, and what would be the effect of prolonging this period. After the experiments with Phyciodes Tharos, which had resulted in a suffusion of colour, the author hoped that some similar cases might be seen in Ajax. The decided changes in 1878 had been produced by eleven and sixteen days’ cold. In 1877, an exposure of two days and three-quarters to eight days had failed to produce an effect.

From these chrysalides 11 perfect butterflies were obtained, 1 male and 10 females. Some emerged crippled, and these were rejected, as it was not possible to make out the markings satisfactorily.

From lot No. 1, fourteen days, came:—

1 female between Marcellus and Telamonides. 2 females, Marcellus.

These 2 Marcellus were pale coloured, the light parts a dirty white; the submarginal lunules on hind wings were only two in number and small; at the anal angle was one large and one small red spot; the frontal hairs were very short. The first, or intermediate female, was also pale black, but the light parts were more green and less sordid; there were 3 large lunules; the anal red spot was double and connected, as in Telamonides; the frontal hairs short, as in Marcellus. These are the most salient points for comparing the several forms of Ajax. In nature, there is much difference in shape between Marcellus and Telamonides, still more between Marcellus and Walshii; and the latter may be distinguished from the other winter forms by the white tips of the tails. It is also smaller, and the anal spot is larger, with a broad white edging.

From lot No. 2, twenty days, came:—

1 female Marcellus, with single red spot.

1 female between Marcellus and Telamonides; general coloration pale; the lunules all obsolescent; 2 large red anal spots not connected; frontal hairs medium length, as in Telamonides.

1 female between Marcellus and Telamonides; colour bright and clear; 3 lunules; 2 large red spots; frontal hairs short.

1 female Telamonides; colours black and green; 4 lunules; a large double and connected red spot; frontal hairs medium.

2 female Telamonides; colours like last; 3 and 4 lunules; 2 large red spots; frontal hairs medium.

From lot No. 3, twenty-five days, came:—

1 male Telamonides; clear colours; 4 large lunules; 1 large, 1 small red spot; frontal hairs long.

1 female Telamonides; medium colours; 4 lunules; large double connected red spot; frontal hairs long.

In general shape all were Marcellus, the wings produced, the tails long.

From this it appeared that those exposed twenty-five days were fully changed; of those exposed twenty days, 3 were fully, 2 partly, 1 not at all; and of those exposed fourteen days, 1 partly, 2 not at all.

The butterflies from this lot of 104 chrysalides, but which had not been iced, were put in papers. Taking 6 males and 6 females from the papers just as they came to hand, Mr. Edwards set them, and compared them with the iced examples.

Of the 6 males, 4 had 1 red anal spot only, 2 had 1 large 1 small; 4 had 2 green lunules on the hind wings, 2 had 3, and in these last there was a 4th obsolescent, at outer angle; all had short frontal hairs.

Of the 6 females, 5 had but 1 red spot, 1 had 1 large 1 small spot; 5 had 2 lunules only, 1 had 3; all had short frontal hairs.

Comparing 6 of the females from the iced chrysalides, being those in which a change had more or less occurred, with the 6 females not iced:

1. All the former had the colours more intense, the black deeper, the light, green.

2. In 5 of the former the green lunules on hind wings were decidedly larger; 3 of the 6 had 4 distinct lunules, 1 had 3, 1 had 3, and a 4th obsolescent. Of the 6 females not iced none had 4, 2 had 2, and a 3rd, the lowest of the row, obsolescent; 3 had 3, the lowest being very small; one had 3, and a 4th, at outer angle, obsolescent.

3. In all the former the subapical spot on fore wing and the stripe on same wing which crosses the cell inside the common black band, were distinct and green; in all the latter these marks were either obscure or obsolescent.

4. In 4 of the former there was a large double connected red spot, and in one of the 4 it was edged with white on its upper side; 2 had 1 large and 1 small red spot. Of the latter 5 had 1 spot only, and the 6th had 1 spot and a red dot.

5. The former had all the black portions of the wing of deeper colour but less diffused, the bands being narrower; on the other hand, the green bands were wider as well as deeper coloured. Measuring the width of the outermost common green band along the middle of the upper medium interspace on fore wing in tenths of a millimetre, it was found to be as follows:

On the iced pupæ 81, 66, 76, 76, 66, 66.

On the not iced 56, 56, 51, 51, 46, 51.

Measuring the common black discal band across the middle of the lower medium interspace on fore wing:

On the iced pupæ 51, 66, 51, 51, 56, 61.

On the not iced 76, 71, 66, 63, 71, 76.

In other words the natural examples were more melanic than the others.

No difference was found in the length of the tails or in the length and breadth of wings. In other words, the cold had not altered the shape of the wings.

Comparing 1 male iced with 6 males not iced:

1. The former had a large double connected red anal spot, edged with white scales at top. Of the 6 not iced, 3 had but 1 red spot, 2 had 1 large 1 small, 1 had 1 large and a red dot.

2. The former had 4 green lunules; of the latter 3 had 3, 3 had only 2.

3. The former had the subapical spot and stripe in the cells clear green; of the latter 1 had the same, 5 had these obscure or obsolescent.

4. The colours of the iced male were bright; of the others, 2 were the same, 4 had the black pale, the light sordid white or greenish-white.

Looking over all, male and female, of both lots, the large size of the green submarginal lunules on the fore wings in the iced examples was found to be conspicuous as compared with all those not iced, though this feature is included in the general widening of the green bands spoken of.

In all the experiments with Ajax, if any change at all has been produced by cold, it is seen in the enlarging or doubling of the red anal spot, and in the increased number of clear green lunules on the hind wings. Almost always the frontal hairs are lengthened and the colour of the wings deepened, and the extent of the black area is also diminished. All these changes are in the direction of Telamonides, or the winter form.

That the effect of cold is not simply to precipitate the appearance of the winter form, causing the butterfly to emerge from the chrysalis in the summer in which it began its larval existence instead of the succeeding year, is evident from the fact that the butterflies come forth with the shape of Marcellus, although the markings may be of Telamonides or Walshii. And almost always some of the chrysalides, after having been iced, go over the winter, and then produce Telamonides, as do the hibernating pupæ in their natural state. The cold appears to have no effect on these individual chrysalides.59

With every experiment, however similar the conditions seem to be, and are intended to be, there is a difference in results; and further experiments—perhaps many—will be required before the cause of this is understood. For example, in 1878, the first butterfly emerged on the fourteenth day after removal from ice, the period being exactly what it is (at its longest) in the species in nature. Others emerged at 19–96 days. In 1879, the emergence began on the ninth day, and by the twelfth day all had come out, except three belated individuals, which came out at twenty, forty, and fifty-four days. In the last experiment, either the cold had not fully suspended the changes which the insect undergoes in the chrysalis, or its action was to hasten them after the chrysalides were taken from the ice. In the first experiment, apparently the changes were absolutely suspended as long as the cold remained.

It might be expected that the application of heat to the hibernating chrysalides would precipitate the appearance of the summer form, or change the markings of the butterfly into the summer form, even if the shape of the wings was not altered; that is, to produce individuals having the winter shape but the summer markings. But this was not found to occur. Mr. Edwards has been in the habit for several years of placing the chrysalides in a warm room, or in the greenhouse, early in the winter, thus causing the butterflies to emerge in February, instead of in March and April, as otherwise they would do. The heat in the house is 19° R. by day, and not less than 3.5° R. by night. But the winter form of the butterfly invariably emerged, usually Telamonides, occasionally Walshii.

Experiments with Phyciodes Tharos.

Exp. 1.—In July, 1875, eggs of P. Tharos were obtained on Aster Nova-Angliæ in the Catskill Mountains, and the young larvæ, when hatched, taken to Coalburgh, West Virginia. On the journey the larvæ were fed on various species of Aster, which they ate readily. By the 4th of September they had ceased feeding (after having twice moulted), and slept. Two weeks later part of them were again active, and fed for a day or two, when they gathered in clusters and moulted for the third time, then becoming lethargic, each one where it moulted with the cast skin by its side. The larvæ were then placed in a cellar, where they remained till February 7th, when those that were alive were transferred to the leaves of an Aster which had been forced in a greenhouse, and some commenced to feed the same day. In due time they moulted twice more, making, in some cases, a total of five moults. On May 5th the first larva pupated, and its butterfly emerged after thirteen days. Another emerged on the 30th, after eight days pupal period, this stage being shortened as the weather became warmer. There emerged altogether 8 butterflies, 5 males and 3 females, all of the form Marcia, and all of the variety designated C, except 1 female, which was var. B.60

Exp. 2.—On May 18th the first specimens (3 male Marcia) were seen on the wing at Coalburgh; 1 female was taken on the 19th, 2 on the 23rd, and 2 on the 24th, these being all that were seen up to that date, but shortly after both sexes became common. On the 26th, 7 females were captured and tied up in separate bags on branches of Aster. The next day 6 out of the 7 had laid eggs in clusters containing from 50 to 225 eggs in each. Hundreds of caterpillars were obtained, each brood being kept separate, and the butterflies began to emerge on June 29th, the several stages being:—egg six days, larva twenty-two, chrysalis five. Some of the butterflies did not emerge till the 15th of July. Just after this date one brood was taken to the Catskills, where they pupated, and in this state were sent back to Coalburgh. There was no difference in the length of the different stages of this brood and the others which had been left at Coalburgh, and none of either lot became lethargic. The butterflies from these eggs of May were all Tharos, with the exception of 1 female Marcia, var. C. Thus the first generation of Marcia from the hibernating larvæ furnishes a second generation of Tharos.

Exp. 3.—On July 16th, at Coalburgh, eggs were obtained from several females, all Tharos, as no other form was flying. In four days the eggs hatched; the larval stage was twenty-two, and the pupal stage seven days; but, as before, many larvæ lingered. The first butterfly emerged on August 18th. All were Tharos, and none of the larvæ had been lethargic. This was the third generation from the second laying of eggs.

Exp. 4.—On August 15th, at Coalburgh, eggs were obtained from a female Tharos, and then taken directly to the Catskill Mountains, where they hatched on the 20th. This was the fourth generation from the third laying of eggs. In Virginia, and during the journey, the weather had been exceedingly warm, but on reaching the mountains it was cool, and at night decidedly cold. September was wet and cold, and the larvæ were protected in a warm room at night and much of the time by day, as they will not feed when the temperature is less than about 8° R. The first pupa was formed September 15th, twenty-six days from the hatching of the larvæ, and others at different dates up to September 26th, or thirty-seven days from the egg. Fifty-two larvæ out of 127 became lethargic after the second moult on September 16th, and on September 26th fully one half of these lethargic larvæ commenced to feed again, and moulted for the third time, after which they became again lethargic and remained in this state. The pupæ from this batch were divided into three portions:—

A. This lot was brought back to Coalburgh on October 15th, the weather during the journey having been cold with several frosty nights, so that for a period of thirty days the pupæ had at no time been exposed to warmth. The butterflies began to emerge on the day of arrival, and before the end of a week all that were living had come forth, viz., 9 males and 10 females. “Of these 9 males 4 were changed to Marcia var. C, 3 were var. D, and 2 were not changed at all. Of the 10 females 8 were changed, 5 of them to var. B, 3 to var. C. The other 2 females were not different from many Tharos of the summer brood, having large discal patches on under side of hind wing, besides the markings common to the summer brood.”

B. This lot, consisting of 10 pupæ, was sent from the Catskills to Albany, New York, where they were kept in a cool place. Between October 21st and Nov. 2nd, 6 butterflies emerged, all females, and all of the var. B. Of the remaining pupæ 1 died, and 3 were alive on December 27th. According to Mr. Edwards this species never hibernates in the pupal state in nature. The butterflies of this lot were more completely changed than were those from the pupæ of lot A.

C. On September 20th 18 of the pupæ were placed in a tin box directly on the surface of the ice, the temperature of the house being 3°-4° R. Some were placed in the box within three hours after transformation and before they had hardened; others within six hours, and others within nine hours. They were all allowed to remain on the ice for seven days, that being the longest summer period of the chrysalis. On being removed they all appeared dead, being still soft, and when they had become hard they had a shrivelled surface. On being brought to Coalburgh they showed no signs of life till October 21st, when the weather became hot (24°-25° R.), and in two days 15 butterflies emerged, “every one Marcia, not a doubtful form among them in either sex.” Of these butterflies 10 were males and 5 females; of the former 5 were var. C, 4 var. D, and 1 var. B, and of the latter 1 was var. C, and 4 var. D. The other 3 pupæ died. All the butterflies of this brood were diminutive, starved by the cold, but those from the ice were sensibly smaller than the others. All the examples of var. B were more intense in the colouring of the under surface than any ever seen by Mr. Edwards in nature, and the single male was as deeply coloured as the females, this also never occurring in nature.

Mr. Edwards next proceeds to compare the behaviour of the Coalburgh broods with those of the same species in the Catskills:—

Exp. 5.—On arriving at the Catskills, on June 18th, a few male Marcia, var. D, were seen flying, but no females. This was exactly one month later than the first males had been seen at Coalburgh. The first female was taken on June 26th, another on June 27th, and a third on the 28th, all Marcia, var. C. Thus the first female was thirty-eight days later than the first at Coalburgh. No more females were seen, and no Tharos. The three specimens captured were placed on Aster, where two immediately deposited eggs61 which were forwarded to Coalburgh, where they hatched on July 3rd. The first chrysalis was formed on the 20th, its butterfly emerging on the 29th, so that the periods were: egg six, larva seventeen, pupa nine days. Five per cent. of the larvæ became lethargic after the second moult. This was, therefore, the second generation of the butterfly from the first laying of eggs. All the butterflies which emerged were Tharos, the dark portions of the wings being intensely black as compared with the Coalburgh examples, and other differences of colour existed, but the general peculiarities of the Tharos form were retained. This second generation was just one month behind the second at Coalburgh, and since, in 1875, eggs were obtained by Mr. Mead on July 27th and following days, the larvæ from which all hibernated, this would be the second laying of eggs, and the resulting butterflies the first generation of the following season.

Thus in the Catskills the species is digoneutic, the first generation being Marcia (the winter form), and the second the summer form. A certain proportion of the larvæ from the first generation hibernate, and apparently all those from the second.

Discussion of Results.—There are four generations of this butterfly at Coalburgh, the first being Marcia and the second and third Tharos. None of the larvæ from these were found to hibernate. The fourth generation under the exceptional conditions above recorded (Exp. 4) produced some Tharos and more Marcia the same season, a large proportion of the larvæ also hibernating. Had the larvæ of this brood been kept at Coalburgh, where the temperature remained high for several weeks after they had left the egg, the resulting butterflies would have been all Tharos, and the larvæ from their eggs would have hibernated.

The altitude of the Catskills, where Mr. Edwards was, is from 1650 to 2000 feet above high water, and the altitude of Coalburgh is 600 feet. The transference of the larvæ from the Catskills to Virginia (about 48° lat.) and vice-versa, besides the difference of altitude, had no perceptible influence on the butterflies of the several broods except the last one, in which the climatic change exerted a direct influence on part of them both as to form and size. The stages of the June Catskill brood may have been accelerated to a small extent by transference to Virginia, but the butterflies reserved their peculiarities of colour. (See Exp. 5.) So also was the habit of lethargy retained.62 The May brood, on the other hand, taken from Virginia to the Catskills, suffered no retardation of development. (See Exp. 2.) It might have been expected that all the larvæ of this last brood taken to the mountains would have become lethargic, but the majority resisted this change of habit. From all these facts it may be concluded “that it takes time to naturalize a stranger, and that habits and tendencies, even in a butterfly, are not to be changed suddenly.”63

It has been shown that Tharos is digoneutic in the Catskills and polygoneutic in West Virginia, so that at a great altitude, or in a high latitude, we might expect to find the species monogoneutic and probably restricted to the winter form Marcia. These conditions are fulfilled in the Island of Anticosti, and on the opposite coast of Labrador (about lat. 50°), the summer temperature of these districts being about the same. Mr. Edwards states, on the authority of Mr. Cooper, who collected in the Island, that Tharos is a rare species there, but has a wide distribution. No specimens were seen later than July 29, after which date the weather became cold, and very few butterflies of any sort were to be seen. It seems probable that none of the butterflies of Anticosti or Labrador produce a second brood. All the specimens examined from these districts were of the winter form.