114 EVOLUTION 



WHY LIKE TENDS TO BEGET LIKE. The 

 fundamental hereditary relation is such that 

 like tends to beget like, and the reason for 

 this is found in the fact of germinal con- 

 tinuity. As long ago as 1875, Galton pointed 

 out that there is a sense in which the child 

 is as old as the parent; for when the parent's 

 body is developing from the fertilized ovum, 

 a residue of unaltered germinal material is 

 kept apart to form the reproductive cells, 

 one of which may become the starting- 

 point of a child. This idea has been in- 

 dependently expressed and more fully de- 

 veloped by Weismann, who states it thus: 

 "In development a part of the germ-plasm 

 [i.e. the essential germinal material] con- 

 tained in the parent egg-cell is not used up 

 in the construction of the body of the off- 

 spring, but is reserved unchanged for the 

 formation of the germ-cells of the following 

 generation." In many cases the future re- 

 productive cells are visibly set apart at a 

 very early stage before the division of labour 

 in body-making has more than begun; in 

 other cases where the future reproductive 

 cells are not visible till much later, we argue 

 by analogy that they are reproductive cells 

 because they have not shared in body- 

 making, but have kept intact the proto- 

 plasmic equipment the full inheritance 



