LARVAL FORMS OF E CH INOD ERM AT A. 491 



scopists have been able to become possessed of it ; but the Author 

 has been fortunate enough to discover a locality (Lamlash Bay, 

 in the Isle of Arran) in which it is so abundant, that it may here- 

 after find its way into almost every cabinet. It has been made 

 next to certain, by the observations of Busch, that this fixed stage 

 is preceded by a free-swimming larval condition ; and the pas- 

 sage from one phase to the other is a problem of the greatest 

 interest, which the Author hopes to have it in his power to work 

 out. 



