293 THE WHENCE AND THE WHITHER OF MAN 



summation of exercise taken during single lives, but 

 upon the summation of more favorable predispositions 

 in the germ." " An organism cannot acquire anything 

 unless it already possesses the predisposition to ac- 

 quire it." * 



We may accept or dgny this last statement, but it 

 is evident that facts like these, and indeed the origin 

 of most or all characteristics involving use or disuse, 

 may be explained almost equally well by either theory. 



But as far as the transmission of effects of somatic 

 changes is concerned, if protozoa undergo special 

 modifications under the influence of external condi- 

 tions, will not the germ-cells undergo special modifi- 

 cation under the influence of changes in the sornato- 

 plasm which forms their immediate environment ? 

 We must never forget the close relationship between 

 all the cells of the body, and how slight a change in 

 the body or its surroundings may conduce to sterility 

 or fertility. Such isolation and independence in the 

 body, on the part of the germ-cells, is opposed to all 

 that we know of the organic unity of the body, whose 

 cells have arisen by the differentiation of, and division 

 of labor between, cells primitively alike. The facts of 

 bud-variation, of changes in the parent stock due to 

 grafting, and others, of which Mr. Darwin has given a 

 summary in the eleventh chapter of the first volume 

 of his "Plants and Animals under Domestication," 

 have never been adequately explained by Weisrnann 

 in accordance with his theory. He has perhaps suc- 

 ceeded in parrying their force by showing that some 

 such explanation is conceivable ; they still point 

 strongly against him. 



* Weismann, Essays, pp. 85 and 171. 



