PRESENT ASPECTS OF EVOLUTION 299 



Wilson lias good reason for his " steadily growing 

 conviction that the cell is not a self -regulating mechan- 

 ism in itself, that no cell is isolated, and that Weis- 

 mann's fundamental proposition is false." 



But, granting the force of these criticisms, the ques- 

 tion still remains, Is the special effect of use or disuse 

 transmissible? Would the blacksmith's son have a 

 stronger right arm ? 



1. The isolation and independence of the germ-cells, 

 which Weismann postulates as opposing this, can 

 hardly be as great as he thinks. 2. It is in his view 

 impossible to conceive how these acquired character- 

 istics can in any way reach and affect the germ-cells 

 in such a manner as to reappear in the next genera- 

 tion. 3. All variations can be explained by his own 

 theory without such transmission. Why then believe 

 that acquired characteristics can in some inconceivable 

 way affect the germ-cells so as to reappear in the next 

 generation, as long as all the facts can be explained 

 in a more simple and easily conceivable manner ? 



As to his second argument, I would readily acknowl- 

 edge that it is at present difficult or impossible for me 

 to conceive how any cell can act upon another, except 

 through the nutrient or other fluids which it can pro- 

 duce. But though I cannot conceive how one cell can 

 affect another, I may be compelled to believe that it 

 does so. And this Weismann readily acknowledges. 



Dries ch changed by pressure the relative position 

 of the cells of a very young embryo, so that those 

 which in a normal embryo would have produced one 

 organ were now compelled, if used at all, to form quite 

 a different one. And yet these displaced cells formed 

 the organ required of cells normally occupying this 



