THE CYCLE OF LIFE 



379 









:' .-r-.-t£!.S-v-^J-;?^, 



^Q^ /S)„ .,v^-^^ 



Fia. 59. — Chain of embryos (b,) of Enoyxtus fusciooUia, all arising from 

 one ovnm, bound together by a chain of mucus (s. ) After Marohal. 



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

 that the germ-cells do not arise from difierentiated 

 body-cells. They are cells which retain intact the 

 quahties of the fertilized ovnm which gave rise to the 

 parent. Similar material to start with, similar conditions 

 in which to develop — therefore, hke tends to beget hke. 

 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 fertihzed 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 Weismami'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- 



