rrof. E. W. MacBride on Echinodenn Lirvv. 477 



LXVI. — Report on a small Collection of Echinoderm Larvce 

 made by Mr. George Murray, F.R.S., during the Cruise of 

 the ' Oceana,' in November 1898. By E. W. MacB .u)k:, 

 M.A., D.Sc, Professor of Zoology in M'Gill University, 

 Montreal. 



All the larv£e wliich I found in the collection were Bipinnarice, 

 and, with the reservations made hereafter, they seem all to 

 belong to the same species, viz. Bipinnaria asferigera (Sars), 

 which is the larva of Luidia Sarsi. 



In the synopsis of all the known species o£ Bipinnaria 

 given by Mortensen {' Die Echiuodermenlarven der Plankton- 

 Expedition ') two species are distinguished from all the rest 

 by the great elongation of the prseoral lobe, or part of the 

 body in front of the mouth, which is bifurcated at the tip 

 into two processes, one belonging to the preeoral and one to 

 the postoral band of cilia. These two species are believed 

 to be the larvse of Luidia Sarsi (Bipinnaria asterigera) and. 

 of Luidia ciliaris respectively. The first of the two species 

 is discriminated from the second by the circumstance that 

 the dorsal process of the prseoral lobe is longer than the 

 ventral and is heart- shaped, being marked on the border by 

 a median indentation. 



All the specimens which are in good enough condition to 

 permit of the determination of these points belong unequivo- 

 cally to Bipinnaria asterigera. Many of them show most 

 distinctly the disk of the future starfish, but in several this 

 is not yet developed. All specimens of Bipinnaria asterigera 

 hitherto described have been late larvae with a well-developed 

 starfish disk; in this collection, for the first time so far as I 

 am aware, the younger stages have been recorded. Where 

 the latei^al and posterior processes of the ciliated rings are 

 preserved they are exceedingly long, so as to deserve the 

 name of tentacles ; but in many specimens they are mutilated, 

 owing possibly to the shaking up they received on their 

 trans- Atlantic journey. 



Garstang, it is true {" Some Bipinnaria from the English 

 Channel," Quart. Journ. Micr. Sc. vol. xxxv.), described a 

 young Bipinnaria which Mortensen considers to be probably 

 a young stage of Bipinnaria asterigera. This I consider 

 possible, but not probable, for the dorsal process of the 

 prseoral lobe is described by Garstang as lanceolate in outline 

 whereas the youngest specimens of B. asterigera in the 

 present collection in which there is not as yet a trace of the 



