SOME BIPINNARI^ iJ^ROM THE ENGLISH CHANNEL. 455 



The dorsal wall of the prae-oral appendage is lined by a dis- 

 tinct longitudinal sheet of elongated mesenchymatous muscle- 

 cells, which are especially well developed in the region of the 

 bend formed by the origin of the anterior dorsal arm from the 

 stalk of the prae-oral appendage. 



2. Habits. 



The larvae were captured a few miles south of the Mewstone 

 at Plymouth. They were taken in tow-nets worked, as a rule, 

 just above the sea bottom ; once or twice they were found in 

 the surface layers of the sea. Many of the forms taken with 

 the larvae were Atlantic animals which rarely visit our shores, 

 but have been unusually abundant this year, probably owing to 

 the prolonged calm and higher temperature of the Channel 

 waters. This fact leads me to imagine that the adult of this 

 form is a starfish living in deep water off the entrance to the 

 English Channel, between the Bay of Biscay and the south 

 coast of Ireland.^ I invariably found the specimens of this 

 Bipinnaria lazily swimming in the upper layers of water 

 in the tall clear glass jars into which 1 have tow-netted 

 material transferred on its arrival at the laboratory. The 

 larvae are almost perfectly transparent and colourless, with the 

 exception of the tips of the posterior lateral arms, which are 

 yellow, and the alimentary tract, which is tinged with yellow 

 and pale brown ; but the slight coloration and opacity which 

 the larvae exhibit are quite sufficient, when associated with 

 their relatively large size and their remarkable mode of swim- 

 ming, to render them conspicuous objects amid the various 

 forms of life associated with them. 



The mode of swimming is quite unique so far as my experi- 

 ence goes. During locomotion, which is usually in an upward 

 direction, the prae-oral lobe is anterior, and the body itself is 

 held quite rigid. Movement is effected by seemingly indolent 



• G. C. Bourne records having taken "several very large Bipinnaria 

 larvse and several later stages in Asterid development " during his cruise 

 off the south-west coast of Ireland, July, 1890. ' Journ. Mar. Biol, Assoc.,' 

 1890, p. 320. 



