INTRODUCTION. XV 



disappears under the teeth of some one or other of these ; 

 and to each kind of debris correspond the instruments 

 suitable for its assimilation. These primary relations 

 between living beings and their alimentary regimen call 

 forth the activity of every species. 



We find, on closer examination, more than one 

 analogy between the animal world and human society; 

 and without much careful scrutiny, we may say that 

 there is no social position which has not (if I may dare 

 to use the expression) its counterpart among the lower 

 animals. 



The greater part of these live peaceably on the fruit 

 of their labour, and carry on a trade by which they gain 

 their livelihood ; but by the side of these honest workers 

 we find also some miserable .wretches who cannot do 

 without the assistance of their neighbours, and who 

 establish themselves, some as parasites in their organs, 

 others as uninvited guests, by the side of the booty which 

 they have gained. 



Some years ago, one of our learned and ingenious 

 colleagues at the University of Utrecht, Professor Hart- 

 ing, wrote a charming book on the industry of animals, 

 and demonstrated that almost every trade is known in 

 the animal kingdom. We find among them miners, 

 masons, carpenters, paper manufacturers, weavers, and 

 we may even say lace-makers, all of whom work first 

 for themselves, and afterwards for their progeny. Some 

 dig the earth, construct and support vaults, clear away 

 useless earth, and consolidate their works, like miners ; 

 others build huts or palaces according to all the rules of 

 architecture; others know intuitively all the secrets of 

 the manufacturers of paper, cardboard, woollen stuffs or 



