ACTIONS OF ANIMALS 353 



generation to generation in the various species or races of animals, 

 without any notable variation so long as no alteration occurs in their 

 environment. 



Of Skill in certain Animals. 



In animals which have no special organ for intelligence, the name skill, 

 apphed to certain of their actions, is scarcely deserved ; for it is only 

 by illusion that we ascribe to them a faculty they do not really possess. 



Propensities acquired and transmitted by reproduction, together 

 with the resulting habits of carrying out complicated actions, in the 

 face of various difficulties which are regularly and habitually overcome 

 by emotions of the inner feeling : these constitute the sum-total of 

 actions, always the same in individuals of the same race, to which we 

 carelessly give the name of skill. 



The instinct of animals consists in the habit of satisfying the four 

 kinds of needs named above, and results from propensities acquired 

 long previously, which constrain to act in a way predetermined for 

 each species. It subsequently happened, in the case of some animals, 

 that a comphcation in the actions required for the satisfaction of these 

 four kinds of needs or of some of them, combined with various difficulties 

 which had to be overcome, gradually forced the animal to increase 

 and develop its methods, and led it to the performance of various 

 new activities, without any choice or act of intelligence, but solely by 

 emotions of the inner feehng. 



Hence the origin in certain animals of various compUcated actions, 

 which people call skill, and which they are never tired of enthusiastically 

 admiring because they always imagine, tacitly at least, that these 

 actions are the result of thought and calculation ; this, however, is an 

 obvious mistake. They are merely the result of a necessity which has 

 developed and guided the habits of animals, until they reach the point 

 at which we find them. 



What I have just said is especially appUcable to the invertebrates, 

 which can carry out no act of intelligence. None of these animals 

 indeed has any power to vary its actions, or to abandon its so-called 

 skill in favour of some other method. 



There is then nothing more wonderful in the alleged skill of the 

 ant-hon {Myrmeleon formica leo) which digs out a hole in loose sand 

 and then waits until some victim falls into the bottom of a hole by the 

 slipping of the sand, than there is in the operation of the oyster, which 

 for the satisfaction of all its needs has only to open shghtly and close 

 its shell. So long as their organisation remains unchanged they will 

 both continue to do just what they do now, without any intervention 

 of will or reasoning. 



