WEISMANN'S THEORY OF THE GERMPLASM 39 



successive divisions, so that the id comes to 

 possess a completely altered architecture. ' Each 

 id in every stage ' (p. 77 of the English edition), 

 ' has its definitely inherited architecture ; its struc- 

 ture is a complex, but a perfectly definite one, 

 which, .originating in the id of germplasm, is trans- 

 ferred by regular changes to the subsequent idic 

 stages. The structure exhibited in all these stages 

 exists potentially in the architecture of the id of 

 germplasm : to this architecture is due, not only 

 the regular distribution of the determinants that 

 is to say the entire construction of the body from 

 its primary form.' 



Unfortunately, Weismann's hypothesis tells us 

 nothing at all about these internal causes, that 

 depend upon the physical nature of the idioplasm ; 

 that is to say, nothing at all about the causes 

 which, working in a fashion so contradictory and 

 astonishing, really produce the whole develop- 

 ment. 



In such a state of affairs it is better to turn to 

 Nature herself, and to see whether or no the 

 occurrence of differentiating division of the nucleus 

 in the organic world is at all supported by the 

 actual observations and investigations of those who 

 study cells. 



We shall examine (1) Unicellular organisms ; 

 (2) Lower multicellular organisms ; (3) The phe- 

 nomena of generation and regeneration ; (4) altera- 

 tion of structural growth due to external inter- 

 ferences (heterornorphosis) ; (5) A nurnber of 

 physiological indications that cells and tissues, in 



