Note 138 — Genus—VERRUCA. Pl. 21.

Mr. Hancock suggests to me that the basal membrane, on the mechanical theory, need not itself move; the motion of epithelial scales, were they transferred into cutting agents, might be supposed to be sufficient. But of such scales, though I used very high powers, I could see no trace; and their presence on the under side of the layer of cement seems hardly possible. Moreover, according to Von Siebold (‘Anatomie Comparée,’ tom. 1, p. 412), ciliary action has not been observed in any Crustacean, or indeed any Articulate animal. This same statement is likewise made in Annals and Mag. of Nat. Hist. 1854, p. 136, by Dr. T. Williams.