VARIATION AND HEREDITY 115 



like tends to beget like, and the reason for this 

 is found in the fact of germinal continuity. 

 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 independently expressed 

 and more fully developed by Weismann, who 

 states it thus : "In development a part of 

 the germ-plasm [i. e. the essential germinal 

 material] contained in the parent egg-cell is 

 not used up in the construction of the body 

 of the offspring, but is reserved unchanged 

 for the formation of the germ-cells of the 

 following generation." In many cases the 

 future reproductive 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 protoplasmic equip- 

 ment the full inheritance of the original 

 fertilized ovum. Thus the parent is rather 

 the trustee of the germ-plasm than the pro- 



