ANIMAL BEHAVIOR. 309 



The " tendency" manifested in some one dog was regarded 

 by Darwin as an accidental variation, the cause being unknown. 

 May not many of the variations appearing in domestic animals, 

 which we call "accidental," be manifestations of instinct roots 

 of more or less remote origin ? 



6. Part Played by Fear. We may now glance once more at 

 the behavior as a whole, for the purpose of pointing out the 

 part played by instinctive timidity. Gentle movements in the 

 water, kept up with steadiness, such as are imparted by a 

 needle in feeding as before described, may induce an attack, 

 while less gentle or unsteady movements may lead the animal 

 to remain quiet or to take flight. The same stimulus, accord- 

 ing to amplitude and evenness, may then be followed either by 

 advance, by quiet, or by retreat. In retreat, fear is manifest ; 

 in quiet it is concealed ; in advance it is less concealed. There 

 can be no doubt that fear predominates in flight and in quiet, 

 while it certainly tempers the advance, giving the appearance 

 of slyness deliberately acted in order to take the prey by sur- 

 prise. This sly manner of advance, whatever it be due to, has 

 a double advantage, for it is concealment against a possible foe 

 and prevents alarming a harmless prey. If I could suppose 

 that fear did not strongly influence the advance, I should 

 certainly incline to think that the animal really appreciated 

 the great advantages in quietly surprising its prey; but for 

 reasons before given I believe the animal is quite blind to any 

 such bearing of its action. The advantages of this manner of 

 action, however, are just the same as if it were deliberately 

 assumed, and the Necturus conducting itself in this way would 

 certainly fare better than one reacting in a contrary way. 

 The instincts of Necturus in this case cooperate to secure 

 its welfare, while if the creature depended upon its intelligence 

 it is difficult to see how it could escape immediate extinction. 



