CIRRIPEDIA. 287 



end : a little behind this are four obtuse bristly processes {h) ; and 

 125 behind them are four little calcareous nodules, or rudi- 

 mental valves. The cavity of the body contains a 

 brownish pear-shaped bag, containing, in some indivi- 

 duals, a mass of spermatozoa. With this testis are con- 

 nected small vesiculae seminales, and Mr. Darwin be- 

 lieves he has distinguished an orifice at the end of the 

 '\^^^y abdomen. After the most careful dissection of very many 

 Supplemental specimens, he can positively affirm that there is no vestige 

 lum vuigare. of moutli or masticatoiy organs, stomach, or intestine.* 



When we reflect on the uniformity of distribution of the Cirripeds, 

 particular species being attached to particular objects, and these not 

 always stationary and extended bodies, but often living animals, and 

 sometimes animals with quick powers of locomotion; when we further 

 call to mind that they adhere, not by prehensile jaws or feet, but by 

 the growth of a pedunculated root, or by the gradual application of a 

 layer of cement forming the base of their shell ; Vv-e must be con- 

 vinced that the organisation and properties of the fettered animal 

 are wholly inadequate to afford an insight into the process by 

 which it acquired its resting-place ; and that a knowledge of the 

 previous career from the time of quitting the egg is not less essential 

 to an explanation of the subsequent attachment of the Cirripedia, 

 than it was for the elucidation of corresponding phenomena in the 

 Ejnzoa, 



No fortuitous dispersion of ova giving origin at once to a pedun- 

 culated or sessile multivalve can account for the invariable attachment 

 of the Coronula to the skin of the whale, and of the Otion to the 

 shell of the parasitic Coronula ; of the Chelonobia to the carapace of 

 the turtle, of the Cineras to the tail of the sea-serpent, or of the im- 

 bedding of the Acasta in the substance of a sponge. Tiiese remark- 

 able phenomena have been explicable only since the discovery of the 

 singular metamorphoses which the Cirripeds undergo, and of the 

 power which they possess, at one period of their existence, of attain- 

 ing and selecting their peculiar and appropriate place of permanent 

 abode. Nor were the real nature and affinities of this singular shell- 

 covered class of animals less problematical and doubtful before the 

 phenomena of their development had been traced out. 



Mr. V. Thompson, whose minute and careful researches into the 

 natural history of marine animalcules have thrown much light on the 

 structure and development of radiated animals, was also rewarded by 

 the discovery of the metamorphosis of the Cirripeds.f On the 28th of 



* CCXXIII. pp. 234, 235. f CCXXV. Memoir iv. 



