60 THE BIOLOGICAL PROBLEM OF TO-DAY 



In the diagram C2 there is actually no median- 

 plane after the third cycle of division. The nuclei 

 9, 10, 14, 13, which in A and B form the right side 

 of the mass, here form a dorsal layer with nuclei 

 7, 8, 12, 11, forming a ventral layer. In the fourth 

 cycle of division the nuclear matter is still more 

 variously distributed through the mass, as may be 

 seen from comparison of diagrams A3, B3, C3. 



Although, under normal conditions, the multi- 

 plication and division of the nuclear material occurs 

 in an almost invariable and definite fashion, the 

 mere altering of the spherical form to a cylinder or 

 to a disc produces a method of division completely 

 different, so far as the nuclei are related to each 

 other in a genealogical tree. In the one and the 

 other method of division the nuclei are brought 

 into relation with different regions of the proto- 

 plasmic mass, and are united with these regions to 

 form cellular individuals. 



I had quite enough reason for what I said in my 

 essay : ' If the doctrine of Roux and Weismann be 

 true, and the successive divisions by which nuclei 

 arise really place different qualities in the nuclei 

 qualities according to which the masses of proto- 

 plasm surrounding them become different and 

 definite parts of the embryo what a pretty set of 

 malformations must result from eggs in which the 

 nuclear matter has been shuffled about so wantonly! 

 As such malformations do not occur, it is plain 

 that the doctrine is untenable.' 



We reach the same conclusion from consideration 

 of the interesting experiments made by Driesch 



