96 



lower limit of the suboral cavity. There is a conspicuous patch of red 

 pigment in the point of the postoral arms. 



The skeleton (Fig. 38) is notable for its smoothness, scarcely an indica- 

 tion of a small thorn being found on any of the rods. The body skeleton 

 forms a basket-structure, the ends of the body rod and recurrent rod 

 having a few irregular branches; but they do not develop into such large, 

 fenestrated plates as is otherwise the rule in Clypeastroid larvae. The 

 postoral rods are fenestrated, the holes being distinctly smaller in the 

 outer part of the rod than in the basal part. The posterodorsal rod appears 



Fig. 38. Skeleton of larva of Clypeaster japonicus; "»/i. A. from the dorsal side, B. side 

 view. To the right of Fig. A the beginning posterodorsal rod is represented separately. 



Letters as in fig. 20. 



to be simple; still a few holes were found at the base, so that perhaps 

 they will be found to be fenestrated to some extent in the fully formed 

 larva. The dorsal arch had not yet appeared in the oldest stage reached. 



Arachnoides placenta (L.) 



PI. X, Fig. 7. 



On an excursion to Napier, New Zealand, on January 29th 1915 I 

 found this species to occur in great numbers in quite shallow water in the 

 lagoon, buried in the sandy mud, generally so deep that not even a slight 

 elevation indicated the place where a specimen was found. As they ap- 

 peared to have ripe sexual products I thought it worth while trying 

 whether I could make an artificial fertihsation, although I had no micro- 

 scope with me, only a pocket lens, and in spite of the fact that I would 



