156 THE STORY OF THE LIVING MACHINE. 



chinery of heredity. This understanding makes 

 the germ substance perpetual and continuous, 



A represents an egg 

 of a starfish. From 

 one half, the unshaded 

 portion, develops the 

 starfish of the next 

 generation, B. The 

 other is distributed 

 without change in the 

 ovaries, ov y of the in- 

 dividual, B. From 

 these ovaries arises the 

 next egg, A\ with its 

 germ plasm. This 

 germ plasm is evident- 

 ly identical with that in 

 A^ since it is merely a 

 bit of the same handed 

 down through the indi- 

 vidual, B. In the de- 

 velopment of the next 

 generation the process 

 is repeated, and hence 

 B' will be like B, and 

 the third generation of 

 eggs identical with 

 the first and second. 

 The undifferentiatecl 

 part of the germ plasm 

 is thus simply handed 

 on from one genera- 

 tion to the next. 



A"' 



FIG. 50. Diagram illustrating the principle of heredity. 



and explains why successive generations are alike. 

 It does not explain, indeed, why an individual in- 



