INTRODUCTION. 1 7 



of each of these categories I propose to arrange the 

 facts in such a way as to bring forward first those 

 animals which, having no special organs, are obliged 

 to exercise the greatest ingenuity, and then to indi- 

 cate the facts which show how variations have arisen 

 which enable other species to accomplish these acts 

 with marvellous ease. 



We will first examine the simplest industries : 

 hunting and fishing, those industries of which the 

 object is the immediate search for prey; and to these 

 may be added those which are related to them as 

 re-action is to action — that is to say, the industries 

 of which the effect is to provide for the immediate 

 safety of the individual. 



Then in an exposition parallel to the march of 

 progress followed by human civilisations, we shall 

 study among animals the art of collecting provisions, 

 of domesticating and exploiting flocks, of reducing 

 their fellows to slavery. 



Finally, we shall investigate the series of modifi- 

 cations which the dwelling undergoes, and we shall 

 see how certain species, after having constructed 

 admirably-arranged houses, know how to make them 

 healthy, and how to defend them against attacks 

 from without. 



