ON THE DEVELOPMENT OF SOME BRITISH ECHINODERMS. 3 



I was right then in maintaining that these later stages figured by Russo 

 could not belong to A. glacialis. 



The most important and interesting contribution to the development 

 of A. glacialis has been given by Yves Delage, who has reared partheno- 

 genetic larvae of this species to full size and beginning metamorphosis.* 

 In spite of this it is still very desirable to make further studies of 

 the normal development of this species. One can, of course, not be sure 

 beforehand that the parthenogenetic larvae are quite like those normally 

 developed. Further, the figures given by Delage are partly not very 

 satisfactory. In fact, it still remains uncertain what the specific char- 

 acters of this larva are, by which it may be distinguished from other 

 Asterias larvse, or whether, perhaps, such characters do not exist, so 



Fig. 1. Fig. 2. 



Figs. 1-2. — Bipinnaria of Asterias glacialis, seven days old. 1, front view ; 



2, side view ; e, enteroccel vesicle. 100/1. 



that this larva could not be distinguished with certainty from other 

 Asterias larvae, for instance that of A. rubens. 



I was very glad then to have the opportunity already on the second 

 day (the 12th June) after my arrival at the laboratory of making an arti- 

 ficial fertilization of A. glacialis. The fertilization was very successful, 

 about 95 per cent of the eggs being fertilized. The culture went on ex- 

 cellently, the larvae being fed with the diatom Nitzschia from Dr. Allen's 

 cultures. However, I did not succeed in obtaining the fully developed 

 larval form. Delage found that the rate of growth of his parthenogenetic 

 larvae was comparatively slow, and I had the same experience with the 

 normal larvae. 



The differentiation of the vibratile chord began after five days, and after 



* Yves Delage, "Elevage des larves parthenogenetiques d' Asterias glacialis" {Arch, de 

 Zool, exper. et gen. (4), II, 1904, jip. 27-46.) 



