194 



second or third day; on the fourth day the embryos were beginning to 

 assume the Bipinnaria-shape. The culture was kept for nearly four weeks 

 apparently in good health (— the larvae kept swimming near the bottom 

 of the dish, not rising to the surface as usual — ); but none of the larvse 

 reached beyond the young Bipinnaria-stage, the enterocoel-pouches not 

 yet at that age having begun prolongating forwards. 



The shape of the Bipinnaria (Fig. 100, C; the specimen figured is 23 days 

 old) does not offer any very marked features distinguishing it from the 

 young larva of Pisaster ochraceus. It is provided with small, yellow pig- 

 ment spots, especially along the vibratile band. 



Orthasterias leptolena Verrill. 

 FertiUzation of this species was undertaken repeatedly in June 1915 at 

 the Biological Station, Nanaimo, but the cultures were not very successful, 

 only in one case the young Bipinnaria-stage being reached. The eggs are 

 of a faint reddish tint; the cleavage stages, blastula and gastrula are very 

 beautiful, perfectly typical. The young Bipinnaria (Fig. 100, D; the spec- 

 imen figured is 7 days old) differs rather considerably from that of the 

 other forms in being broadly rounded in the anterior end; the vibratile 

 band is not developed along the anterior edge of the body, which indicates 

 almost certainly that the larva will develop into a Brachiolaria. 



Pycnopodia helianthoides (Brandt). 



This large and strikingly beautiful Asterid, which occurs quite com- 

 monly at Nanaimo, was found to have its breeding season in May — June. 

 Fertilization was undertaken repeatedly, but a good culture never resulted. 

 The embryos never reached more than just beyond the gastrula stage. All 

 the information acquired of the development of this species thus amounts 

 only to this that it has pelagic larvae ; but what they look like or whether 

 they have a Brachiolaria-stage remains an open question. 



As stated above (p. 185) the material of pelagic Echinoderm larvae found 

 in the plankton samples includes a number of Bipinnariae, among which 

 some interesting new forms which would very well deserve to be figured 

 and described. Unfortunately, they are nearly all of them in a poor state 

 of preservation, so that it is hardly possible to give a reconstruction of 

 their true shape. I have therefore thought it better to desist from describing 

 them here. Only one form I shall briefly mention, viz. the larva in the 

 Brachiolaria-stage represented in PI. XXXIII, Fig. 7. It affords the inter- 



