312 HISTORY OF BRITISH CRUSTACEA. 



of foot-jaws of two joints, and not like a sucking- disc. 

 Segments of thorax uncovered. Body more or less oval, 

 depressed. Eyes two, close together : in the living animal, 

 of a red colour, and slightly projecting. 



The species of this family are found on various fishes in 

 the sea. They adhere to the body among the scales, being 

 attached by their foot-jaws. They can move to any part of 

 the fish. They die soon after the fish is taken from the 

 water. There seems to be some doubt as yet about their 

 food. The most minute observers seem to think that it is 

 chiefly, if not wholly, on the mucous juices of the fishes 

 that they subsist, those juices which cover the body of the 

 fish, and for secreting which in abundance there are, in most 

 fishes, a series of particular pores. The fishes on which they 

 are found are generally weak and diseased. The young 

 CallgidcB, when first hatched, are very different in appear- 

 ance from the adult : they closely resemble the young of the 

 Cgclopidtf, and undergo, like them, a number of changes of 

 skin before they assume the completely-developed form of 

 the parent. 



