12 Professor Gregg Wilson on 



or is changed. Weismaim's attempt to refer all such changes to 

 re-combinations of internal factors in the germ-plasm itself has 

 not met with much success. Admitting that new combinations 

 may be brought about in this way, yet it seems unlikely that the 

 entire process of evolution could have resulted by re-combining 

 what already existed ; for it would mean, if taken at its face 

 value, that by re-combination of the differences already present 

 in the first living material, all of the higher animals and plants 

 Avere fore-ordained." 



In this connection it is worth while to quote Bateson, our 

 great Mendelian worker, who writes : " As to almost all the 

 essential features whether of cause or mode l)y which specific 

 diversity has become what we perceive it to be, we have to 

 confess an ignorance almost absolute." 



A third difficulty in the way of believing in the "all- 

 sufficiency of natural selection " is found in the fact that the 

 mechanistic theory of development by " evolutio " makes no real 

 attempt to explain the orderly arrangement of the wonderful 

 units that are supposed to exist in the germ-plasm. As Child 

 says :* " The combination of these units into the individual is 

 assumed to occur as the facts demand, and although the problem 

 of the co]]trol and ordering of millions of such units through all 

 the changes involved in the development of a complex organism, 

 say the human body, is one which staggers human intelligence, it 

 is practically ignored." 



But a fourth difficulty arises from the fact that there is now 

 good reason to say that development is not an " evolutio." And 

 Weismann's whole system depends on this doctrine. Roux at 

 one time seemed to have confirmed the view that the germ-plasm 

 is a mosaic and development a mere displaying of characters that 

 were localised in the egg. He destroyed one cell of a two-cell 

 stage in a frog's development, with the result that a half-embryo 

 developed. But with sea-urchin eggs Driesch got opposite 

 results : one cell of a two-cell stage, or even of a later stage, was 

 * " Individuality of Organisms,"' pp. 22-23. 



