CHAP. IX. CIKRIPEDIA AND EHIZOCEPHALA. 



95 



Chonos Islands. The egg, which 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 Sacculina 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 few words 

 upon the earliest pro- 

 cesses in the develop- 

 ment of the Crustacea. 

 Until recently it was re- 

 garded as a general rule 

 that, by the partial seg- 

 mentation of the vitel- 

 lus a germinal disc was 

 formed, and in this, cor- 



16 Figs. 61 63. Eggs of Tetradita porosa in segmentation, magn. 

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

 always turned towards the pointed end of the egg. Fig. 64. Egg of 

 Lernscodiscus Porcellanx, in segmentation, magn. 90 diam. 



U3 



Figs. 61, 62, 63, 64. 



