240 



THE EVOLUTION OF SEX. 



elements ? Weismann's answer is a decided negative. Although 

 no continuous chain of germ-like cells is demonstrable, there is 

 a strict continuity oi (j^Qx\T\-plas}na. Part of the double nucleus 

 of the fertilised ovum keeps its characteristics unaltered, in spite 

 of manifold divisions persists intact, and is finally established 

 in the rudiment of reproductive organs. Or in other words, 

 those cells in which the original germ-plasma most predominates 

 become the reproductive cells. To quote Weismann's own 

 words, " In each development a portion of the specific germ- 

 plasma which the parental ovum contains, is not used up in 

 the formation of the offspring, but is reserved unchanged to 



The cluoiiiatin elements of the nuclei in coil («), douljle star (/'), and almost 

 divided stages (c). — After Pfitzner. 



form the germ-cells of the following generation." In short, con- 

 tinuity is kept up by the plasma of nuclei, rather than by a chain 

 of cells. It will be observed, of course, that while early insul- 

 ation of definite germ-cells is a demonstrable fact, to be seen 

 in a few cases, though perhaps of wider occurrence than we 

 know of, the continuity of germ-plasma is strictly an hypothesis. 

 This being so, reproductive maturity may be defined as the 

 period when the reproductive cells (bearing the inherited capital 

 of germ-plasma) have established themselves to that degree 



