SOME JAPANESE ECHINODERMS. 



549 



Pig. 2. — Sketches showing the variation in shape of the larva of Laganum 



75 



dccagonale. — 



of the egg. The larval skeleton is, of course, rudimentary, but is 

 otherwise in accordance with the typical skeletal structure of 

 Clypeastroid-larvae. 



It is worth pointing out that, in spite of the large size of the 

 eggs, the cleavage is total and quite regular. A feature not hitherto 

 seen in Echinoids, if I remember aright, is that the embryo in the blastula 

 stage, before it leaves the egg-membrane, has the ectoderm strongly 

 folded, much as it occurs in some starfishes {Ltiidia a.o.). The forma- 



