THE CIRRIPEDIA 



chambers on the inner and outer surfaces, receiving respectively 

 branches of the ovaries of the Cirripede and prolongations of the 

 epidermal tissue of the host. 



The base of the shell in the Operculata may be simple and 

 membranous or it may become calcified, and in the latter case it 

 may be traversed by radial canals (Fig. 64, c.r) carrying prolonga- 

 tions of the hypodermis. 



In Xenobalanus (Figs. 65, 66) among the Operculata the wall is 

 reduced to a small vestige and the opercular" plates are absent. 

 The mantle-sac is elongated and appears as if divided into capitular 



and peduncular portions, giving the 

 animal an extraordinarily close re- 

 semblance to certain Pedunculata such 

 as Alepas. 



It may be mentioned here that in 

 the Pedunculate Anelasma, which is 

 parasitic on sharks, the peduncle 

 becomes imbedded in the muscles of 



CL+I 



Fio. 65. 



Xenobalanus 

 B, the reduced "wall"; p, 



Fio. 66. 



Diagram of the reduced " wall " of Xeno- 

 "balanus. C, carina ; C.L+L, carino-lateral 



penis. (From Gravel's Mono- fused with lateral; /<./,, rostro-lateral ; R, 



graphif.) 



rostrum. (From Gravel's Moiiogmphie.) 



the host and gives off minute ramifying filaments which no doubt 

 serve for the absorption of nutriment. 



The body, enclosed within the mantle, consists of a cephalic 

 region ("prosoma" of Darwin), followed by a "thoracic" region 

 corresponding to the somites bearing the six pairs of cirri. These 

 somites are usually indistinctly defined in the membranous integu- 

 ment and the first is always coalesced with the head. There is no 

 distinct "abdomen" in the adult except in so far as it is repre- 

 sented by the caudal furca which is present in most Pedunculata 

 and. a few Operculata. The f urcal rami are usually small, unjointed 

 or with few segments. Exceptionally they may be long and multi- 

 articulate. 



Appendages. The antennules, which serve for attachment in the 

 larva, usually persist in a functionless condition imbedded in the 

 cement which fastens the end of the peduncle or the base of the 



