148 Heredity. 



is possible to believe that the transmission uf variabil- 

 ity is the peculiar function of the male cell, and also to 

 acknowledge that variation may occasionally occur with- 

 out its influence. 



Our theory that variation is caused by the transmis- 

 sion of gemmules, and that there is no especial ariange- 

 ment for their transmission to buds or to unfertilized 

 eggs, while there is a special adaptation which has been 

 slowly evolved during the evolution of sex for transmit- 

 ting them to fertilized eggs, gives us a simi)le ex})lana- 

 tion of the fact that while bud variation is perfectly pos- 

 sible, it is extremely rare as compared with the variabil- 

 ity of sexual offspring. 



Darwin has been led, through the study of variabil- 

 ity, to a conclusion which is very much like the expla- 

 nation which is here presented. He says {Variation, 

 Vol. ii. p. 325) that '^we may infer from the occurrence 

 of bud variation that the affection of the female element 

 through external conditions may induce variability, for 

 a bud seems to be the analogue of an ovule. But the 

 male element is apparenthj much oftener affected ly 

 changed conditions, at least in a visible manner, than 

 the female element or ovule.^^ 



Bud variation is much more frccpient in cultivated 

 plants than it is in wild ones. A^ery few instances have 

 ever been observed in plants growing wild or under 

 strictly natural conditions, and Darwin states that " bud 

 variation is most common in jilants which have been 

 highly cultivated for a long time." 



The adjustment between a cultivated organism and its 

 artificial or unnatural environment must, in most cases, 

 be less perfect than that which has been slowly estab- 

 lished between a wild organism and its natural environ- 

 ment. We should, therefore, expect domesticated and 



