PLANKTON FROM NEW BRUNSWICK. 



287 



anterior lobe which carries them in the Ascidian larva, as a 

 preoral lobe (" Studies on the Protochordata," 1893, Quart. Journ. 

 Micro. Sci. vols. 34 & 35) ; a suggestion which the late W. K. 

 Brooks was unable to accept. 



Apart, however, from questions of morphology, the comparison 

 between the three adhesive processes of Brachiolaria and those of 

 the Ascidian tadpole cannot fail to be appropriate. I am not 

 aware that it has been made before. 



Th. Mortensen (' Die Echinodermenlarven der Plankton- 

 Exped.' 1898) figured the Brachiolaria of the European Asterias 

 i'ubeits, and adds that it is so much like that of A. vulgaris that a 

 separate description is unnecessary : but as the one larva occurs on 

 the North American coasts, and the other on the North European 

 coasts, no confusion is possible. I do not know of any data 

 which would enable a distinction to be made between the larva 

 of A. vulgaris and that of the associated species, A.forbesii. 



Semidiagrammatic view of Brachiolaria attached to a piece of seaweed. 



The larva swims through the \yater with the three anterior 

 bipinnarian arms curving backwards, the remaining eight bipin- 

 narian arms trailing behind. The anterior medio-doisal adhesive 

 process is directed forwards ; the lateral adhesive processes may 

 be bent forwards or backwards. The median pi-ocess develops in 

 advance of the lateral processes and is already formed, with its 

 contained branch of the hydroccel, whilst the lateral processes 

 are represented by rudimentary ectodermal thickenings with a 

 minute projection of the hydrocoel below each of them. 



