72 



ANIMAL PARASITES AND MESSMATES. 



Fig. 2 — Ricinus of the Pygarg-- 



Fishes harbour crustaceans 

 instead of ticks, and their num- 

 ber is not less considerable than 

 on mammals and birds. These 

 crustaceans have perplexed na- 

 turalists more than once, be- 

 cause they could only regard them 

 as parasites. They live on the 

 produce of cutaneous secretions, 

 and if they improve, as do the 

 ticks, the cleanliness of their host, 

 they are not less useful in a 

 hygienic point of view, for they 

 prevent the accumulation of cuta- 

 neous productions. 



Among these crustaceans, we 

 must mention the Caligi and the Arguli, which never 

 become bloated, the Ancei, and probably other genera. 

 Instead of the ungainly and unusual forms of true 

 parasites, they all preserve, together with their fishing 

 tackle and locomotive apparatus, their neat and elegant 

 appearance. The sexes even differ only in size. They 

 remain during the whole of their life what they are at 

 the beginning ; that is to say, charming in form, with a 

 delicately-shaped corselet, numerous and slender claws, 

 and are as graceful in their movements as when in a 

 state of rest. The greater number of osseous fishes lodge 

 Caligi on the surface of their skin. These fix themselves 

 by means of strong cables, but without sacrificing their 

 liberty. They are usually called fish lice. 



Fishermen, when returning from the northern 

 fishery, generally find their vivarium full of 'these 



