THE ORIGIN AND DEVELOPMENT OF ORGANISMS 333 



the individual is simply the unfolding of a bit of it, the soma- 

 plasm, which is set aside to develop into an individual for the 

 purpose of carrying for future generations the germ plasm which 

 is to continue the race. Heredity is thus due to the continuity 

 of the germ plasm from generation to generation. 



It is seen that, in accordance with this theory, heredity is 

 simply a name given to a process of handing on from age to 

 age a bit of marvelous material, the germ plasm, small bits of 

 which have the property of developing into individuals. As 

 long as this germ plasm is handed on unchanged, it will pro- 

 duce a succession of generations identical with each other, and 

 there will be a conformity of type. It will be seen thus that 

 the child does not actually inherit anything from its parents; 

 the child and parent are alike because both develop characters 

 that are present in the continuous germ plasm. 



Variations in Germ Plasm are Inherited. It is evident that 

 any modification of the germ plasm must permanently affect 

 the race. If at any period the germ plasm should be changed 

 so as to produce in it a new character, the new character will 

 inevitably appear, not only in the next generation, but in the 

 following generations. Characters which appear in the germ 

 plasm at once become, therefore, race characters, handed on with 

 certainty, unless something subsequently causes their disappear- 

 ance from the germ plasm. 



Variation in the Individual not Inherited. It is equally evi- 

 dent that any variation occurring in the body, but not in the 

 germ plasm, will have a very different effect upon the race. 

 The individual is only a trustee of the germ plasm which is 

 stored away somewhere in his body. Among animals, the germ 

 substance is largely stored away in the ovaries and sperm 

 glands; among plants it may be more distributed, but here 

 also it is probably located in certain parts of the plant. If 

 we admit that the individual has nothing to do with this germ 

 substance except handing it on to the subsequent generations, 

 it is evident that no special change which affects the individual 



