adjoining sketch Fig. 13 (which was not drawn with the 

 camera). I may state that I found the same peculiar 

 membrane-formation in Sir. drobachiensis (by a fertil- 

 ization made at the same time, which, however, did 

 not result in any rearing of the larvae, the breeding 

 season of that species being then already past, only 

 few eggs remaining); 1 regret not having noticed whether 

 the same phenomenon occurs in Str. pulcherrimus. 



The gastrula stage was reached after about 2-1 hours, 

 and in the course of the next day the embryos had 

 assumed the shape of young Plutei. The poslero-dorsal arms began to 

 appear at the age of <S days. IJeyond this stage I did not succeed in 

 rearing the larva 1 , the culture dying oil when the larva 1 were 12 days 



Fig. 1I5. Egg in the 

 l-ci'll stage of Str. 

 franciscanus: show- 

 ing double nieni- 

 brane. 



old. A new fertilization 



Fig. 14. Skeleton of larv;i 

 Strongylocentr. /ranciscanu*. I 

 stage. Side view. 300 /,. 

 Letters as in fig. .">. 



was tried in the later part of June, but then 

 the breeding season was past and only few 

 eggs could be found, which did not develop 

 normally. However, I can give some informa- 

 tion also of the fully formed larva of Str. 

 frtincificanus, having found a specimen in the 

 plankton. As no other species of Kchinoids 

 occur there, besides Denilraslcr exceniricus - 

 the larva of which 1 have also reared, and 

 which has no resemblance to the present larva 

 - and a Spatangoid, Brisaster lalifrons (A. 

 Ag.) which was not ripe and which has, 

 moreover, probably not pelagic- larva - there 

 cannot be any doubt that this larva really 

 belongs to Str. franciscanus. 



The larva of S. fnincisniinix in its first stage 

 dillers from that of drobuchicnsis and pulcher- 

 rimus in the posterior end of its body being 

 distinctly less elongated and more rounded 

 (I J 1. IX, Figs. 1 3). The arms are not so broad 

 as in the said species. As in these species the 

 body skeleton does not form a basket struc- 

 ture. The body rod is clubshapecl, rather 

 strongly thorny at thv thickened end, which 

 curves somewhat inwards: it is distinctly 

 shorter than in the two other species. Further- 

 more this larva differs from the two other 

 larva? known of this genus in having a well 







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