PARASITES FREE WHILE YOUNG. 145 



The Iones thoracicus, the Cepes distortus, the Gyges 

 bramchialis, and so many others live, like the Bopyri, 

 in the thoracic cavity of different decapod crustaceans, 

 and the females throw off at the same time their organs 

 of sense and all their fishing and travelling apparatus. 



Eathke, a learned professor of Konigsberg, was 

 the first to notice an isopod, known under the name 

 of Phryxus p&gwri, which lives on the stomach of a 

 pagurus, attached to it by its back, so that the stomach 

 of the parasite is turned, like that of the pagurus, 

 towards the partitions of the shell. The tail with the 

 branchial appendages is always directed towards the 

 orifice of the shell. The male is very small and never 

 leaves the female. The Athelca cladophora is another 

 bopyrian living on the abdominal region of a pagurus, 

 which always chooses shells infested by Alcyonia. 

 Another bopyrian, the Prosthetes cannelatus, lives on the 

 abdomen of an ordinary pagurus. 



Mons. Bucholz has recently described a new kind 

 of isopod, allied to the lyriopes, which lives on the 

 Hemioniscus. This isopod fixes itself 

 to a Balanus (B. ovularis), and the 

 female preserves only four of her seg- 

 ments with their appendages : she had 

 fifteen, when young. Thus she throws 

 off nearly all her appendages which 

 have become useless. The male of 

 this isopod, which inhabits the bay 

 of Christiansand, is not yet known. %».-aT»»'M- 



* kei. A figure of the 



Another parasite of this group has natural size is given 



been observed by Fr. Miiller at Des- atthe8ide - 



terro, on the coast of Brazil. It bears the name of 



