GENETICS 103 



ditions, in the body or in its own cytoplasm, and 

 the limitation of gene action to the including cell 

 would seem to be inevitable. The results of gene 

 action might contribute to the environment of 

 other cells, but this effect could hardly be associ- 

 ated with the formative influence exerted by a gene 

 within the cell. 



Wherever we drop the problem it leaves a feeling 

 of tantalizing uncertainty and in my own thoughts 

 the persistence of a horde of unused, inactive 

 genes in every cell of the body is the most serious 

 diflSculty. There is no evidence that any part of 

 the chromosome complex in any cell loses its 

 potentiality. Weismann's idea of differential dis- 

 tribution of the nuclear elements has not only been 

 overthrown by cytological evidence, but also 

 replaced with opposite evidence that there is no 

 such differentiation. There are some cases of cell 

 modification which bear out this view thoroughly, 

 the most important being the origin of germ cells 

 from somatic tissues. The chromosomes of the 

 germ cells alone must be complete. There is not 

 the slightest possibility that a cell without a com- 

 plete assortment of genes may develop into a 

 complete individual. Yet specialized tissues in 

 plants may give rise to germ cells, and a few cases 

 among animals indicate the same transformation. 

 Fell 27 has shown that in cases of sex-reversal in 



» Brit. Joum. Exp. Bid., Vol. I, p. 97. 1923. 



