WEISMANN' 8 THEORY OF THE GERMPLASM 55 



the cells, and that the cells may be pushed over one 

 another like a heap of balls without disturbing in 

 the slightest their capacity to develop. Such a 

 permutation could be without injury to the develop- 

 mental product only if one nucleus had the same 

 qualities as another ; that is to say, only if all the 

 nuclei had arisen from the nucleus of the fertilized 

 egg by doubling division. 



Driesch is right to regard these experiments as 

 incompatible with Weismann's theory. ' Only 

 consider,' he remarks, ' how great a number of 

 " supplemental hypotheses," how many " accessory 

 determinants," would be required to make speci- 

 fication of the early stages of a development in 

 which any nucleus may take the place of any other 

 nucleus in the whole embryo/ 



I myself have carried out similar experiments 

 upon frogs' eggs experiments with a double in- 

 terest. The frog's egg has the poles different, and 

 so has a definite orientation. Weismann and Eoux 

 themselves have used these objects to support their 

 view that, at the first cleavage, nuclei with different 

 qualities are formed. 



On p. 64 of the English edition Weismann 

 remarks : ' The fact that the right and left halves 

 of the body can vary independently in bilaterally 

 symmetrical animals points to the conclusion that 

 all the determinants are present in pairs in the 

 germplasm. As, moreover, in many of these 

 animals e.g., in the frog the division of the 

 ovum into the two first embryonic cells indicates a 

 separation of the body into right and left halves, 



