OBSERVATIONS ON MAMMALS 241 



and that this sense has become so fixed an instinct as 

 to be transmitted to the offspring and to have de- 

 veloped in them the same instinctive fear though they 

 themselves have endured no persecution. If any man 

 could persist in the domestication of duc'.s or rabbits 

 commencing from the wild stock, I have no doubt 

 that he would eventually rear offspring as tame as the 

 rabbits of the rabbit-hutch or the ducks of the poultry- 

 yard. 



The tail of the flying squirrel is worth attention. 

 It is long, thick and bushy. Its functions are two in 

 number ; the one is its use as a warm covering to 

 surround the head and body during sleep, the other 

 is its employment as an agent to secure the animal's 

 balance in the trees. 



I used to amuse myself by placing the squirrel on a 

 smooth bar to see how the tail was exerted to maintain 

 the creature's balance. The squirrel sits clutching the 

 bar. Its claws cannot penetrate the surface, so that 

 it must use all its powers of balance to keep its 

 equilibrium. The tail hangs vertically down behind ; 

 it is rigid, definitely held in that position for a special 

 purpose. I draw the animal's head forward and up 

 goes the tail to increase the counterpoise behind. 

 I pull the hind quarters backward and the tail is swept 

 forward beneath the bar and equilibrium is restored. 

 I push the squirrel to the left and the tail is inclined 

 to the right ; I push it to the right and the tail turns 

 to the left. Any movement of the animal in one 

 direction is met with a counterbalance of the tail in 

 the opposite direction, and a uniform equilibrium is 

 thus attained. 



This function of the tail is illustrated in another 



R 



