THE DEVELOPMENT OF ASTERINA GIBBOSA. 343 
of the Asterid and Crinoid to their common ancestor were 
designed for me by my friend and colleague Mr. J. J. Lister, 
of St. John’s: in their present form they were drawn for me by 
a lady friend. 
The Development of the Larva. 
The eggs are laid by the parent on the under surface of 
stones, to which they adhere by means of their vitelline 
membrane. I have never discovered a male, though Ludwig 
says that the male twists his arms round the female whilst she 
is depositing her ova, and then pours out his spermatozoa 
upon them; it is quite certain that in the English Channel, 
at any rate, isolated females will lay eggs which develop with 
perfect regularity up to the conclusion of the metamorphosis. 
Cuénot (4) says that young females of a certain size develop 
spermatozoa in their ovaries—a statement I have not been able 
to verify. It may, indeed, be said that Ludwig’s statement that 
a kind of sexual congress takes place, Cuénot’s observations, 
and the experience of the authorities of the Jersey Biological 
Station are irreconcilable, and that the whole subject demands 
renewed investigation. 
The eggs are larger than those of most other Echinoderms ; 
they are about ‘5 mm. in diameter. This is a result of the 
yolk which they contain, and which gives them their bright 
orange colour. This yolk is so uniformly distributed, however, 
that it does not alter the type of segmentation, which is total 
and regular. The blastomeres, in consequence of their larger 
size, are more closely packed than is usual amongst Echino- 
derms; they are wedged into the interspaces between their 
neighbours, and so the strict “ radial’’! type of segmentation 
characteristic of the group is no longer maintained. 
The result of segmentation is a hollow blastosphere or 
blastula, which on the second day of development becomes 
converted into a gastrula by embolic invagination, The embryo 
1 For a discussion of the different types of regular segmentation see “ The 
Cell-lineage of Nereis,” by Prof. E. B, Wilson, ‘Journal of Morphology,’ 
vol. vi. 
