146 ANIMAL PARASITES AND MESSMATES. 



Entoniscus porcellanse. The parasite which he discovered 

 by the side of it on the same animal, and to which he 

 has given the name of Lerneoniscus, had perhaps in- 

 troduced it. We have seen examples of this kind 

 among insects. Among the rich materials which Pro- 

 fessor Semper brought back from his voyage, there was 

 a Porcellana, which harbours on its exterior surface a 

 very remarkable isopod, whose recurrent development 

 is no less decided than that of the peltogasters. Dr. 

 Kausmann has lately described these curious organisms, 

 to which he has given the name of Zeuxo. Another 

 isopod, with a no less decided recurrent development, 

 has received from the same naturalist the name of 

 Cahira Lerneodiscoides. 



We now come to an isopod which aims higher : he 

 doubtless considers that cray-fish and crabs walk too 

 slowly for him ; he therefore addresses himself to a fish, 

 the Puntius maculatus, which inhabits the river Tykerang 

 (Bandong) in Java. This isopod is called Ichthoxenus 

 Jellinghausii. This isopod crustacean, living at first in 

 the same manner as the rest, looks out for a small 

 cyprinoid fish, thrusts itself like a trocar behind the 

 abdominal fins, through the scaly skin, and penetrates 

 entirely into the abdominal cavity. The male always 

 accompanies its female. It is remarkable that she, in 

 contradistinction to many others, preserves all the attri- 

 butes of her sex. She does not change her form more 

 than the other free crustaceans of her order, and. only 

 differs from the male in size. It is well known that in 

 all these animals the male is always smaller than the 

 female. Mons. Jellinghaus, Who first described this 

 crustacean, observed that all fishes which he caught had, 



