THE CYCLE OF LIFE 



379 



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FIG. 59. Chain of embryos (E,)of Encyrtus fuscicollis, all arising from 

 one ovum, bound together by a chain of mucus (s. ) After Marchal. 



segregation of the germ-cells is not demonstrable, we know 

 that the germ-cells do not arise from differentiated 

 body-cells. They are cells which retain intact the 

 qualities of the fertilized ovum which gave rise to the 

 parent. Similar material to start with, similar conditions 

 in which to develop therefore, like tends to beget like. 

 Two famous quotations may make this fundamental fact 

 of germinal continuity quite clear. There is a sense, Galton 

 said, 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. To use Weismann's words : ' 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- 



