148 Heredity. 



is possible to believe that tlie transmission of 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 arrange- 

 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 simple explana- 

 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 

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

 male element is apparently much oftener affected ly 

 changed conditions, at least in a visible manner, than 

 the female element or ovule." 



Bud variation is much more frequent in cultivated 

 plants than it is in wild ones. Very 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 plants 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 



