452 WALTER GAESTANG. 



In October, 1846, a swarm of these Bipinnarise visited 

 Bergen harbour, and formed the material for some researches 

 by Drs. Koren and Danielssen (1). These naturalists pointed 

 out the real nature of the connection between the starfish and 

 the Bipinnaria. Two preserved specimens of these Bipin- 

 narise subsequently came into the hands of Johannes MUUer, 

 and an account of them is included in the second of Miiller^s 

 memoirs (2). 



So far as I am aware,^ no specimens of this interesting larva 

 have been captured since 1846. During the month of August 

 this year, however, I have taken near Plymouth a number of 

 Bipinnaria larvse which resemble Sars's larva in many points. 

 At the same time they show some differences which seem to 

 be important. It may eventually be proved that these dis- 

 similarities are due to a different stage of development ; or, on 

 the other hand, the Plymouth larvae may be shown to belong 

 to a type of Asterid distinct from that to which Sars's larva 

 belongs. Up to the present time, however, I have not suc- 

 ceeded in finding specimens in which there is any trace of 

 approaching metamorphosis, so that the identification of the 

 larva has not been possible. 



1. Structure. 



A glance at the figures on Plate 28 reveals at once the 

 fact that the Plymouth larvae are constructed upon a plan 

 which is intermediate between that of Sars^s Bipinnaria 

 asterigera and the more common type of starfish larva. 

 They agree with the former in exhibiting a great development 

 of the prse-oral lobe; while they resemble the commoner type, 

 and at the same time differ from Sars's larva, in the less con- 

 centrated arrangement of the paired ciliated arms. 



The primitive circumoral ciliated ring is divided as usual 

 into two distinct portions, one of which borders the ventral 

 side of the prse-oral lobe (figs. 1 and 2, a. c. o. b.) ; while the 

 other {p. c. o. b.) not only borders the dorsal side of the prae- 



' Metschnikoff, I find, made use of this larva in his researches on intra- 

 cellular digestion. Vide ' Quart. Journ. Mic. Sci.,' xxiv, 1884, p. 99. 



