24 



latter species has not the peculiar shape of a biconvex lens, and the post- 

 oral arms are not horizontal, and, upon the whole, it appears that the 

 larvae of these two forms must be very unlike. The horizontally directed 

 postoral arms of Eucidaris Thouarsi, which must doubtless be much 

 longer in the fully formed larvae, recall the remarkable Echinopluteus 

 Iransuersus; were it not for the ophicephalous pedicellariae of the latter, 

 I would think them to belong together. The few facts brought 

 forward here can only make one the more anxious to get an opportunity 

 of working out the complete development of Eucidaris. That, at least, 

 E. metularia has a similar larval form is very probable. Its eggs are quite 

 similar to those of E. Thouarsi, as I was able to ascertain during my 

 stay at Hilo, Hawaii. Fertilization of this species could, however, not 

 be undertaken, as I never succeeded in getting a ripe male and female 

 at the same time. 



While the larva of Cidaris cidaris is the only Cidarid-larva hitherto 

 reared to what must be at least very nearly its full shape, it is quite pos- 

 sible that also the larva of another Cidarid, viz. Stylocidaris af finis (Phil.) 

 is known. As I have explained in my paper on "Die Echiniden des Mittel- 

 meeres" 1 ) there is some reason to think that the larva figured by Job. 

 Mil Her in his 7th Memoir on the larvae and metamorphosis of Echino- 

 derms, Taf. I Fig. 1 2, belongs to this Cidarid, not to Sphserechinus, as 

 was hitherto supposed. 



Phyllacanthus parvispinus Ten. Woods. 



PL V. Figs. 34. 



During a short stay at Port Jackson in the beginning of March 1915 

 I found a few specimens of this species containing ripe genital products 

 and I succeeded in getting a small culture. The eggs are few in number, 

 rather large, ca. 0.5 mm, of a greenish colour, and they float at the sur- 

 face. The fertilization membrane is very thick, gelatinous, not sharply 

 limited on the outside. The first division was seen to take place about 

 3 hours after fertilization. As the fertilization was undertaken in the 

 evening the process of the cleavage could not be followed in details, 

 only a very poor light being available. It appeared, however, that the 



cidaris papillata, so that I have been able to confirm that it is really this species, which was 

 studied by Prouho, not the more common mediterranean form, Slylocidaris afflnix. which 

 was at the time Prouho wrote his paper not recognized as separate from Cidaris cidaris. 



l ) Th. Mort ensen. Die Echiniden des Mittelmeeres. Eine revitlierte Ubersicht der 

 im Mittelmeere lebenden Echiniden init Beinerkungen iiber neue oder wenig bekannte For- 

 men. Mitt. a. d. Zool. Stat. Neapel. 21. 1913. p. 20. 



There is, however, also a possibility that this larva may belong to Genocidaris macnlala 

 A. Ag., the larva of this common mediterranean species being also unknown. 



