SOME BIPINNARI#. FROM. THE ENGLISH CHANNEL. 451 



On some Bipinnariae from the English 

 Channel. 



By 



l¥alter Oarstang', M.A., 



Fellow of Lincoln College, Oxford, Naturalist to the Marine Biological 

 Association. 



With Plate 28. 



The genus Bipinnaria was defined by the elder Sars (3) 

 in the following terras : — " Corpus gelatinosum longum cylin- 

 drico-depressum, pinnis duabus, una postice terminali cordi. 

 formi, altera triangulari in medio corpore. Os appendiculis 

 seu brachiis lanceolatis circumdatura/^ To this genus he 

 referred the single species asterigera, " appendicibus seu 

 brachiis 12 circa os." 



Few zoologists meeting with this passage for the first time 

 would, I imagine, recognise in it the description of a starfish 

 larva; for the Bipinnaria of the text-books is invariably of 

 that simpler, commoner, and smaller type which formed the 

 basis of Johannes Miiller's classical researches. The original 

 Bipinnaria of Sars was a remarkably elongated creature, 

 fully one inch in length, with a crown of polyp-like tentacles 

 at the oral end of the body, a bilobed fin at the other extremity, 

 and a median ventral fin placed transversely ; attached to the 

 tentaculate end of the body was a small five-rayed starfish. 

 Sars himself was so puzzled by the animal that he referred it, 

 not without some natural hesitation, to a special group of 

 Acalephse. 



