58 HEREDITY 



consequence of the fact that no two parts {e.g. physio- 

 logical units or determinants) of the mother-germ- 

 cell were subject to precisely the same forces. This 

 plainly recalls the Weismannian explanation — " in- 

 equalities of nutrition." 



Thus we are prepared to understand that the 

 essence of variation is a novelty in the cell-divisions, 

 by which the mother-germ-cell, or germ-mother-cell, 

 gives rise to the "germ-daughter-cells," and these 

 to the "germ-granddaughter-cells," which are the 

 gametes, or germ-cells, themselves. This novelty is 

 a deduction, in the pages of Spencer, from the law 

 of the instability of the homogeneous. Forty years 

 later we find Professor Bateson saying, in a Presiden- 

 tial Address to the Zoological section of the British 

 Association (1904), that " variation is a novel cell- 

 division " : that is, a novel cell-division during the 

 process of gametogenesis. Bateson's assertion did 

 not depend on the validity of Spencer's deduction 

 of 1864, but was based upon the work of the Abbe 

 Mendel and his recent followers — work which we 

 shall consider in the next chapter. 



But even now we have not yet adduced all the 

 reasons for looking up the pages of Spencer before 

 passing to the consideration of Mendelism. For 

 Spencer goes on to say, in the paragraph from which 

 I have already quoted,^ that another fact in the link 

 of events which determines variation is the " segre- 

 gation which inevitably goes on in any mixed aggre- 

 gate of units and prevents a homogeneous mean 

 between the two parents." The existence of this 

 segregation in the case under consideration is 



1 "Principles of Biology," § 88. 



