196 



% 



lend themselves very easily to artificial fertilization nor to breeding in 



aquaria. I was not prepared to use that method during my voyage, partly 

 because my former experiments with Holothuria nigra did not make clear 

 to me the difficulties generally met with in the study of the development 

 of Holothurians by means of artificial fertilization, partly because it would 

 have been rather troublesome to carry along such a live-box on the long 

 voyage. 



As is the case with the Asteroid-larvae, the larvae of the Holothurians 

 are as a rule not found very well preserved in plankton samples, and the 

 material which I have gathered in that way is not very important, present- 

 ing no new larval types. The contribution to the knowledge of the Holo- 

 thurioid-larvae which I can give here, is accordingly rather small, especially 

 as compared with that of the Echinoid- and Ophiuroid-larvee. 



Stichopus californicus (Stimpson). 



PI. XXXIII, Figs. 89. 



This species, which occurs fairly commonly along the rocky shores near 

 the Biological Station at Nanaimo, was found to have ripe sexual products 

 in June. Fertilization was undertaken repeatedly and with good success, 

 though the percentage of the fertilized eggs was always rather small. I 

 have no notices about the first developmental processes, except that the 

 embryos were found in the blastula stage one day, in the gastrula stage 

 two days after fertilization; the formation of the Auricularia may begin 

 on the second day. At the age of about 6 days the larvae were typical 

 Auriculariae, provided with a starshaped calcareous body in the left postero- 

 lateral process. In this stage the larvae remained till the age of ca. 3 weeks, 

 no further development taking place. 



The shape of the larva (PI. XXXIII, Figs. 89) 

 is somewhat elongated. The preoral band is highly 

 arched ; there are no preoral processes, but the frontal 

 area is distinctly constricted at the level of the upper 

 end of the oral cavity, the anterior part forming a 

 Fig. 101. Spicuies trom rounc } et i lobe; the corresponding part on the dorsal 



larva of Stichopus call- . 



fornicus. >M / t . The small slc ' e 1S much narrower. The dorsal and posterolateral 

 spicuie to the right from lobes are fairly distinct. The postoral band is strongly 



the right posterolateral , ,1 i 



process convex in the middle so as almost to suit the shape 



of the preoral band. The anal area is markedly con- 

 stricted at the lower end of the body, the posterior edge of which is 

 distinctly concave. The calcareous body (Fig. 101) has the shape of an 

 irregular star; very rarely there is a small, irregular calcareous body also 



