XXIV INTRODUCTION. 



The assistance rendered by animals to each other is 

 as varied as that which is found amongst men. Some 

 receive merely an abode, others nourishment, others 

 again food and shelter ; we find a perfect system of 

 board and lodging combined with philozoic institutions 

 arranged in the most perfect manner. But if we see by 

 the side of these paupers, some which render to one 

 another mutual services, it would be but little flattering to 

 them to call all indiscriminately either parasites or mess- 

 mates {commensaux) . We think that we should be more 

 just to them if we designated the latter kinds rnutualists, 

 and thus mutuality will take its place by the side of mess- 

 tahle arrangements {commensalism) and of parasitism. 



It would also be necessary to coin another name for 

 those which, like certain crustaceans, or even some birds, 

 are rather guests which smell out a feast from afar 

 (pique-assiettes) than parasites ; and for others which 

 repay by an ill turn the assistance which they have 

 received. And what name shall we give to those which, 

 like the plover, render services which may be compared 

 to medical attendance ? 



This bird in fact performs the office of dentist to the 

 crocodile. A small species of toad acts as an accoucheur 

 to his female companion, making use of his fingers as 

 a forceps to bring the eggs into the world. Again, the 

 pique-boeuf performs a surgical operation, each time 

 that he opens with his lancet the tumour which encloses 

 a larva in the midst of the buffalo's back. Nearer home, 

 we see the starling render in our own meadows the 

 same service as the pique-boeuf {Buphaga) in Africa ; and 

 we may see that among these living creatures there is 

 more than one speciality in the healing art. 



