MKTAMORI'HOSrS OV CORVSTES OASSI VlilI,AUN[JS. 461 



The Metamorphosis of Corystes Cassivelaunus 



(Pennant). 



By 

 Kobei-t Ouriiey, B.A.(Oxoii.), F.Z.S. 



With Plates 29—31. 



The material upon wliicli tlie following account of the 

 development of Corystes is based lias been derived entirely 

 from tow-net collections, taken generally in or just outside 

 Plymoutli Sound, between February and May of the present 

 year. Occurring first on February 21st, the larvse were 

 obtained in small numbers fairly regularly from that time 

 onwards. Advanced stages occurred first on March 15th, 

 and in considerable numbers. The tow-net collections of 

 April 14th, taken in the West Channel, were remarkable for 

 the extraordinary abundance of the zotea stage of Corystes. 

 They abounded on that date to the almost complete exclusion 

 of all other zoeeas, nearly all the specimens being at an 

 advanced stage of development. Since April 14tli the 

 zoEeas have continued to occur, but very few have been 

 found in the early stages. 



Zoseas taken in the tow-nets have been kept successfully 

 in plunger jars for considerable lengths of time, and several 

 have moulted into the Megalopa stage, the latter being kept 

 through the next moult, either in a jar immersed in running 

 water or in a beaker, in which the water was kept in motion 

 by a stream of air bubbles. 



