NARRATIVE OF THE CRUISE. 



389 



lengthened, and thinned ont and depressed so as to form four deep, thin-walled, oval cups 

 sinking into and encroaching upon the cavity of the test, and forming very efficient pro- 

 tective ' marsupia ' (fig. 144). The ovarial openings are, of course, opposite the inter- 



Frc. 144. — Hemiaster cavernosus (Phil.). 

 The apical portion of the test of the female 

 seen from within. Slightly enlarged. 



Fin. 146.— Bemiaster cavernosus (Phil.). 

 The apical portion of the test of the male 

 seen from within. Slightly enlarged. 



)hM 



radial areas ; but the spines are so arranged that a kind of covered passage leads from the 



opening into the marsupium ; and along this passage the eggs, which are remarkably 



large, upwards of a millimetre in diameter when 



they leave the ovary, are passed, and are arranged 



very regularly in rows on the floor of the pouch, 



each egg being kept in its place by two or three 



short spines which bend over it (fig. 146). 



" Among the very many examples of this Hpmi- 

 aster which we dredged in Accessible Bay, and 

 afterwards in Cascade Harbour, Kerguelen, there 

 were young in all stages in the breeding pouches ; 

 and although from the large size and the opacity 

 of the egg and embryo it is not a very favourable 

 species for observation, had other conditions been 

 favourable] we had all the material for working 

 out the earlier stages in the development of the 

 young very fully. The eggs, on being first placed 

 in the pouches, are spherical granular masses of a 

 deep orange colour, enclosed within a pliable vitel- 

 line membrane, which they entirely fill. They become 

 rapidly paler in colour by the development of the 

 blastoderm; they then increase in size probably 

 by the imbibition of water into the gastrula-cavity ; and a whitish spot with a slightly 

 raised border indicates an opening which, I have no reason to doubt, is the permanent 



Fig. 146. — Bemiaster cavernosus i Phil.). The arrange- 

 ment of the eggs in one of the marsupial recesses. 

 Five times the natural size. 



