Note 4 — Chapter XII · PROGRESS OF EVOLUTION IN CRUSTACEA.

Whether the want of the abdominal feet in the young of Tanais be an inheritance from the time of the primitive Isopoda, or a subsequently acquired peculiarity, which appears to me the more admissible view at present, may perhaps be decided with some certainty, when we become acquainted with the development and mode of life of its family allies, Apseudes and Rhœa. The latter, as is well known, is the only Isopod which possesses a secondary flagellum on the anterior antennæ. I have recently obtained a new and unexpected proof that the Tanaidæ (“Asellotes hétéropodes” M.-Edw.) of all known Crustacea approach most closely to the primitive form of the Edriophthalma. Mr. C. Spence Bate writes to me: “Apseudes, as far as I know, is the only Isopod in which the antennal scale so common in the Macrura is present on the lower antenna.”