REPRODUCTION. 679 



likewise a so-called native kind which was formerly intro- 

 duced from South America. All these plants belong to the 

 same species and are alike in appearance, but the Cochineal 

 insect flourishes only on the native kind." 



Weismann and those who agree with him in denying 

 the influence of changes in the conditions of life in causing 

 variation, maintain that variation is wholly dependent upon 

 crossing. We have already pointed out that this view fails 

 to account for Adaptation, and we will now briefly suggest 

 other objections to it. In the first place, as we have already 

 learned, variation may occur quite independently of sexual 

 reproduction, in the form of bud-variation. In the second 

 place it appears that crossing does not, in the case of wild 

 plants, lead to the appearance of new characters, that is, to 

 variation ; though this is apparently the case with species 

 which have been already rendered in some degree variable 

 by cultivation. Gartner states, for instance, that when he 

 crossed native plants which had not been cultivated, he never 

 saw in the offspring any new character. Now if, as Weis- 

 mann insists, variation is simply a new combination of old 

 characters, why is it that cross-fertilisation leads to it in 

 cultivated but not in wild plants ? The more reasonable 

 view seems to be, that the variation of cultivated plants is 

 the expression, not of a recombination of old characters, but 

 of the acquisition of new in virtue of their high variability ; 

 and that variation is less common in wild plants because they 

 are less variable than cultivated plants. 



We conclude then that the production of varieties is the 

 result of the influence of the conditions of life. These con- 

 ditions act upon the whole protoplasm of the individual, and 

 affect therefore those portions of its protoplasm which the 

 individual throws off as reproductive cells. The modification 

 is less readily transmitted by sexual than by asexual repro- 

 duction, when only one of the parents has been modified in 

 the particular manner, for the modifications transmitted by 

 the modified parent are, as it were, toned down by the in- 

 fusion of protoplasm from the unmodified parent. But, as 

 already mentioned, when both parents are similarly modi- 



