136 ARE THE EFFECTS OF USE INHERITED? 



would enlarge or perfect it. Teeth, claws, nails, 

 skin, hair, hoofs, feathers, &c., may thus be worn 

 away faster than they can renew themselves. 

 But this wearing away usually stimulates the 

 repairing process, and so increases the rate of 

 growth ; that is, it will increase the size produced, 

 if not the size retained. Which effect of use does 

 use-inheritance transmit in such cases the in- 

 creased rate of growth, or the dilapidation of the 

 worn-out parts ? We can hardly suppose that 

 both these effects of use will be inherited. Would 

 shaving destroy the beard in time or strengthen 

 it ? Will the continued shearing of sheep 

 increase or lessen the growth of wool ? What 

 will be the ultimate effect of plucking geese's 

 quills, and of the eider duck's abstraction of the 

 down from her breast ? If the mutilated parts 

 grow stronger or more abundantly, why were 

 the motmot's feathers alleged to be narrowed by 

 the inherited effects of ancestral nibbling ? 



