154 THE EVOLUTION THEOKY 



the contrary, the butterflies fly a great deal, just as all other diurnal 

 ' butterflies do; they exert their power of flight as long as the sun shines, 

 and if the exercise of one generation influences the next, they ought to 

 become gradually more capable of rapid flight. In this case exactly the 

 opposite takes place to what is ascribed to the Lamarckian principle ; 

 more constant use must here have brought about a diminution of the 

 activity of the relevant parts. It is quite otherwise when we look at 

 it from the point of view of selection. The variants which cropped 

 up by chance with slower flight survived because they were most 

 easily recognized and avoided ; they are the most frequent survivors ; 

 they leave descendants which inherit the slower flight-instinct, and this 

 goes on increasing in them as long as the increase carries any 

 advantage with it. As soon as this ceases to be the case the variation 

 comes to a standstill, for it is adapted to the average of the conditions 

 at a given time. 



We may picture to ourselves the thousand kinds of regulations of 

 animal movements through instinct as having come about in a similar 

 way ; in the majority of cases we iniust picture it thus. For it is only 

 in the case of those with high intelligence that we can ask whether 

 the animal did not by deliberation help in establishing the purposive 

 variation in its movements. Among insects in any case this could only 

 be taken into account to a very limited extent, although I do not 

 dispute that the more intelligent among them may learn, and may 

 make experiments, and can modify their actions accordingly. But in 

 fleeing from an enemy experience has nothing to do with it, for the 

 first time it is caught it pays the penalty with its life. Without care, 

 and with no idea of the dangers surrounding them on all sides, the 

 butterflies float about, guided only by their instinct, which, however, 

 is so exactly adapted to the conditions of their life that a sufficient 

 number of them to preserve the species always happily escapes all the 

 many dangers. I may remind you of Hahnel's case of the butterfly, 

 already mentioned, which escaped the agile lizard by flying rapidly 

 up from the sweet bait, but settled again upon it without fear 

 immediately afterwards, to fly from the lizard as before, and did so 

 several times in succession. We usually judge such actions far too 

 much from the human standpoint ; the butterfly does not wish to 

 escape the death which threatens it ; it knows nothing about death ; 

 it is not with it as it was with Dr. Hahnel himself, who when he was 

 once in danger from a jaguar in a thicket was so afiected by the 

 thought of the death he had happily escaped that he never cared to 

 pass the place again, but made a long circuit to his home. The 

 butterfly does not act according to reflection and imagination ; it flies 



