178 THE STORY OF LIFE'S MECHANISM. 



Now whether this undifferentiated germ plasm, 

 as we will now call it, is distributed all over the 

 body, or is collected at certain points, is im- 

 material to our purpose. It is certain that por- 

 tions of it find their way into the reproductive 

 organs of the animal or plant. Thus we see 

 that part of the chromatin material in the 

 egg of the first generation develops into the 

 second generation, while another part of it 

 remains dormant in that second generation, 

 eventually becoming the chromatin of its eggs 

 and spermatozoa. Thus each egg of the second 

 generation receives chromosomes which have 

 come directly from the first generation, and thus 

 it will follow that each of these eggs will have 

 identical properties with the egg of the first 

 generation. Hence, if one of these new eggs de- 

 velops into an adult, it will produce an adult 

 exactly like the second generation, since it con- 

 tains chromosomes which are absolutely identical 

 with those from which the second generation 

 sprung. There is thus no difficulty in under- 

 standing why the second generation will be like 

 the first ; and since the process is simply repeated 

 again in the next reproduction, the third genera- 

 tion will be like the second, and so on, generation 

 after generation. A study of the accompanying 

 diagram will make this clear. 



In other words, we have here a simple under- 

 standing of at least some of the features of here- 

 dity. This explanation is that some of the chro- 

 matin material or germ plasm is handed down 

 from one generation to another, and is stored 

 temporarily in the nucleii of the reproductive 



