238 METAMORPHOSIS AND 



hormones affect the determinants in the gametes. 

 But it is obvious that the black and white of Leghorn 

 fowls and of guinea-pigs are gametogenic characters, 

 and are strongly established in the gametes of their 

 respective varieties. It is not even certain that the 

 black or white hair or feathers are giving off special 

 hormones which would or could influence the 

 gametes. The hormone theory only postulates such 

 influence from hormones issuing from tissues modified 

 by external stimuli. It is quite certain that the 

 black colour in Leghorns or guinea-pigs is not due 

 to any external stimulus or influence. The experi- 

 ments therefore are entirely irrelevant to what has 

 been called the inheritance of acquired characters. 

 AU that they can be said to prove is that an albino 

 soma does not convert ingrafted ova of black race 

 into ova carrying the albino character. 



It is probably impossible to prove experimentally 

 the influence of a modified soma in one generation. 

 I have endeavoured to find a case which would not 

 be open to the above criticism — that is, to find a 

 character which could be considered somatogenic and 

 which was absent in a closely allied variety. Most 

 of the characters in domesticated varieties are 

 obviously gametogenic mutations, but the lop-ear in 

 rabbits may be, partly at least, somatogenic. Since 

 many breeds have upright ears, we cannot say that 

 disuse of the external ear has produced lop-ears in 

 domesticated rabbits generally, but in lop-eared 

 breeds the ears are much enlarged ; and though this 

 may be gametogenic, the increased weight may 

 have been the cause of the loss of the power to erect 

 the ears. I therefore tried grafting ovaries from 

 straight-eared females into lop-eared individuals. 



