MUTUALIST3. 



gi-caceful vermin. It may be said 

 that the caligi are common every- 

 where, and that each species has 

 its own caHgi. The fishes of 

 the family Plagiostoma, notwith- 

 standing the hardness of their 

 skin, afford food to some of these ; 

 they multiply so rapidly some- 

 times, that they cover their host 

 as though they took the place of 

 scales. The cod gives lodging to 

 a charming species of a very 

 beautiful shape, which in its turn, 

 affords a resting-place to the 

 Udonella. It is always attached 

 to the ovisacs, and doubtless plays 

 the same part as the Histriobdellse, 

 so that we shall find the CaHgi 

 ^ attending to the toilet of the cod, 

 and the Udonellae in their turn 

 waiting on the Caligi. 



The name Argiili has been 

 given to some crustaceans which 

 resemble the caligi in size and in 

 manner of life, and which prin- 

 cipally frequent fresh-water fishes. 

 The Argulus foliaceus is the name 

 of the species which has 

 been known for the longest 

 time, and which is most 

 extensively found. It is to 

 be seen on our pikes, carps. 



Of the natural 

 size. 



Caligulvs el^gans 

 (feni.) 



