224 



every circumstance that attends the marches of these 

 birds. The degree of cold or heat that accelerates, or 

 retards them, deserves to be particularly attended to ; 

 for there is no room to doubt that they are most of 

 all influenced by this. There is, perhaps, a secret rela- 

 tion between the temperature which suits with certain 

 species, and that which is necessary for the production 

 of the food that nourishes them. 



But we have not tarried our enquiries deep enough 

 into these different species of birds and fishes of passage. 



10. An-ong the soc eties of brutes Improperly so 

 called, some depend on chance, or on the agency of 

 men, if not altogether, at least in part It is not so with 

 respect to societies properly so called. They do not 

 owe \heir origin to any human act, but solely to nature, 

 Thewiembers that compose them are not only united 

 by common necessities, and that for a short time, but 

 they are so by a much stronger tie, which subsists to 

 tjje dea)h of the animal, or at least during a consider- 

 able ?>art of its life ! 1 mean, the natural preservation 

 of the individual, or that of its family : both the one 

 and the other are necessarily attached to the state of 

 society. It is for this great end that these different 

 species of social animals have been instructed to labour 

 in common on works so worthy of admiration. 



Societies properly so called may be divided into two 

 classes: the first comprehends those whose principal end 

 is limited to the preservation of individuals , the second^ 

 those whose scope is the preservation of individuals, and 

 education of their young. 



Several species of caterpillars, and some species of 

 worms, belong to the former of these two classes ; ants, 

 wasps, bees, beavers, to the second. 



The first class will have under it two principal sorts ; 

 one of which will comprehend temporary societies ; the 

 r, societies for life. 



