CERRIPEDIA. 



429 



sist of a swollen body, which projects from the host through 

 an aperture on the ventral surface, and of a system of roots 

 which ramify through the tissues of the host (Fig. 277). As 

 in the case of the Cirripedia Genuina the structure of the 

 adult is best elucidated by the study of development. 



FIG. 276. Consecutive larval stages of Sacculina carcini (from Lang, after Delage). A, 

 nauplius after first moult ; B, free swimming Cypris-stage ; C, Cypris-stage after the larva 

 has become attached to a seta (b b) of the host ; D, formation of the Kentrogon larva ; E, 

 the Kentrogon larva after the Cypris shell has been thrown off and the pointed process 

 formed ; F, the process has pierced the cuticle of the host. 



1, 2, 3 the nauplius limbs ; I- VI the thoracic limbs of the Cypris stage ; ab abdomen ; 

 66 seta of the host ; / fat globules ; fs frontal sensory organ ; gl glands of the frontal 

 horns ; ov rudiment of the ovary ; pf pointed process ; ua nauplius eye. 



Much light has been thrown on the structure and life-history of this 

 group by the admirable researches of Yves Delage on Sacculina carcini 

 Thomps. In the nauplius larva (Fig. 276, A) the mouth and alimentary 

 canal are absent, but a mass of " primitive ova " can already be distin- 

 guished. In the Cypris stage the antennae are prehensile and bear two 

 large sense organs, and the 6 pairs of biramous swimming legs are well 

 developed. After swimming freely for two or three days the larva attaches 



