76 MIND IN EVOLUTION CHAP. 



act of walking as distinct from the purpose with which we 

 set out is for every one but an infant a true compound 

 reflex. The contact of the foot with the ground sets in 

 motion a number of waves of excitement directed in part 

 to maintaining the balance, in part to the onward move- 

 ment. The resulting contractions bring the other foot 

 forward, and the result is a fresh contact, setting similar 

 contractions to work, and so forth. 1 



This familiar instance may serve to illustrate the general 

 plan of a compound reflex, and to show that there is 

 nothing to prevent a train of action of considerable com- 

 plexity being carried on through a succession of responses 

 each following with rigid and predetermined uniformity 

 upon its proper stimulus. Where an u instinct " is of this 

 character, it may be made to betray itself by some slight 

 variation in the circumstances which render the action 

 useless or injurious. When we apply this test we get 

 some very strange results, and what at one moment we 

 take for instinctive behaviour of a high order seems at 

 another to sink to mechanical action of a rigid type. A 

 well-known observation by M. Fabre will illustrate my 

 point. 2 



. . . " A solitary wasp, Sphex flavipennis^ which provisions its 

 nest with small grasshoppers, when it returns to the cell, leaves 

 the victim outside, and goes down for a moment to see that all is 

 right. During her absence M. Fabre moved the grasshopper a 

 little. Out came the Sphex, soon found her victim, dragged it to 

 the mouth of the cell, and left it as before. Again and again 

 M. Fabre moved the grasshopper, but every time the Sphex did 

 exactly the same thing, until M. Fabre was tired out." 3 



1 Walking is subject to the permanent disposition to go forward. In 

 purposive acts such a disposition exerts a controlling influence from the 

 background which is roughly parallel to that exerted by the permanent 

 condition in the instinctive series. But subject to this condition the acts 

 involved in walking as long as everything is straightforward are, I think, 

 reflex. The slightest obstacle, of course, brings consciousness into play. 



In low organisms movements of the whole body may be analysed into 

 chain reflexes in which the activity of one part stimulated from without 

 is itself the stimulus to the appropriate act of the next part, and so on. 

 (S. J. Holmes, Phototaxis in the Sea-urchin, J.A.B. p. 135.) 



2 Lubbock, Senses of Animals, p. 245. 



* It does not follow that the wasp was destitute of intelligence, or that 

 it is not under any circumstances able to bring intelligence to bear on the 

 action. Indeed, a subsequent experiment of Fabre's on another individual 



