Chap. IX. CIRRIPEDIA AND ßHIZOCEPHALA. 



95 



Clionos Islands. The egg, whicli is at first elliptical, 

 soon, according to Darwin, becomes broader at the 

 anterior extremity, and acquires three club-shaped 

 horns, one at each anterior angle and one behind ; no 

 internal parts can as yet be detected. Subsequently 

 the posterior horn disappears, and the adherent feet 

 may be recognised within the anterior ones. From this 

 " egg-like larva " — (Darwin says of it, " I hardly know 

 what to call it ") — the pupa is directly produced. Its 

 carapace is but slightly compressed laterally and hairy, 

 as- in SaccuUna purpurea ; the adherent feet are of con- 

 siderable size, and the natatory feet are wanting, as, in 

 the adult animal, are the corresponding cirri. As I 

 learn from Mr. Spence Bate, the Nauplius-stage appears 

 to be overleaped and the larvae to leave the egg in the 

 pupa-form, in the case of a Khizocephalon {Peltogaster ?) 

 found by Dr. Powell in the Mauritius. 



I will conclude this general view with a iew w^ords 

 upon the earliest pro- ..^^^ 

 cesses in the develop- /^U^ 

 ment of the Crustacea. 

 Until recently it w^as 

 garded as a general rule 

 that, by the partial seg- üiV/k^^^^ 

 mentation of the vitel- 1 ^J 



lus a germinal disc was 

 formed, and in this, cor- 



64 



Figs. 61, 62, 63, 6i. 'G 



16 Figs. 01 — 63, Eggs of Tetradlta porosa in segmentation, magn. 

 90 diam. The larger of the two first-formed spheres of segmentation is 

 always turned towards the pointed end of tlie ej 

 Lernsiodiscus Forcellanx, in segmentation, magn. 90 diam. 



