108 THE DESCENT OF MAN 



actions are performed whether they are due to instinct, or 

 to reason, or to the mere association of ideas: this latter 

 principle, however, is intimately connected with reason. A 

 curious case has been given by Prof. Mobius," of a pike, 

 separated by a plate of glass from an adjoining aquarium 

 stocked with fish, and who often dashed himself with such 

 violence against the glass, in trying to catch the other fishes, 

 that he was sometimes completely stunned. The pike went 

 on thus for three months, but at last learned caution, and 

 ceased to do so. The plate of glass was then removed, but 

 the pike would not attack these particular fishes, though he 

 would devour others which were afterward introduced; so 

 strongly was the idea of a violent shock associated ia his 

 feeble mind with the attempt on his former neighbors. If 

 a savage, who had never seen a large plate-glass window, 

 were to dash himself even once against it, he would for a 

 long time afterward associate a shock with a window-frame; 

 but, very differently from the pike, he would probably re- 

 flect on the nature of the impediment, and be cautious under 

 analogous circumstances. Now with monkeys, as we shall 

 presently see, a painful or merely a disagreeable impression, 

 from an action once performed, is sometimes sufficient to 

 prevent the animal from repeating it. If we attribute this 

 difference between the monkey and the pike solely to the 

 association of ideas being so much stronger and more per- 

 sistent in the one than the other, though the pike often re- 

 ceived much the more severe injury, can we maintain in the 

 case of man that a similar difference implies the possession 

 of a fundamentally different mind? 



Houzeau relates" that, while crossing a wide and arid 

 plain in Texas, his two dogs suffered greatly from thirst, 

 and that between thirty and forty times they rushed down 

 the hollows to search for water. These hollows were not 

 valleys, and there were no trees in them, or any other differ- 

 ence in the vegetation, and as they were absolutely dry there 



»» "Die Bewegungen der Thiere," etc., 18'J3, p. 11. 



** "Facult^s Mentales des Animaux," 18'J2, torn. ii. p. 265. 



