284 SEXUAL RELATIONS OK 



the parasite is destitute of these same organs, though 

 present in the parasites of S. rostratum and S, Peronii. 

 Again, S. villosum approaches, in all its characters, very 

 closely to the genus Pollicipes, and the parasite in having 

 prehensile antennae, with the disc but little pointed, and 

 with spines at the further end, departs from Scalpellum 

 and approaches Pollicipes ! Will any one believe that 

 these several parallel differences, between the Cirripedial 

 parasites and the Cirripedes to which they are attached, are 

 accidental, and without signification ? yet, this must be 

 admitted, if my view of their male sex and nature be 

 rejected. 



One more, and the most important special relation 

 between the parasites and the cirripedes to which they are 

 attached, remains to be noticed, namely that of their 

 prehensile larval antennae. I observed the antennae more 

 or less perfectly in the males of all, and except in S. vil- 

 losum, in all the species, though so utterly different in 

 general appearance and structure, I found the peculiar, 

 pointed, hoof-like discs, which are confined, I believe, to 

 the genera Ibla and Scalpellum. In the hermaphrodite 

 forms of Scalpellum, I was enabled to examine the antennae 

 only in two species, S. vulgare and S. Peronii, (belonging, 

 fortunately, to the two most distinct sections of the genus,) 

 and after the most careful measurements of every part, I 

 can affirm that, in B. vulgare, the antennae of the male and 

 of the hermaphrodite are identical ; but that they differ 

 slightly in the proportional lengths of their segments, and 

 in no other respect, from these same organs in S. Peronii, 

 — in which again the antennae of the male and of the her- 

 maphrodite are identical. The importance of this agree- 

 ment will be more fully appreciated, if the reader will con- 

 sider the following table, in which the generic and specific 

 differences of the antennae in the Lepadidae, as far as 

 known to me, are given. These organs are of high func- 

 tional importance ; they serve the larva for crawling, and 

 being furnished with long, sometimes plumose spines, they 

 serve apparently as organs of touch • and lastly, they are 

 indispensable as a means of permanent attachment, being 



