INTRODUCTION 15 



angles. From this continuous stream of germplasm 

 there split off at successive intervals complexes of so- 

 matoplasm, or "individuals," which go so far on the 

 road of specialization into tissues that the power to 

 be "born again" is lost, and so after a time they die, 

 while the germplasm, held in reserve, lives on. 



This is what is meant by saying that a father and 

 son owe their mutual resemblance to the fact that they 

 are chips off the same block rather than by saying that 

 the son is a chip off the paternal block. Both somato- 

 plasms are developments at different intervals from 

 the same continuous stream of germplasm instead of 

 one somatoplasm derived from a preceding one. As 

 a matter of fact the germplasm from which the son 

 arises is modified by the addition of a maternal contri- 

 bution, so that father and son in reality hold the same 

 relation to each other that half-brothers do. 



So far as his body or his somatoplasm is concerned, 

 the son is younger than his father but at the same time 

 he is older than his father in his germplasm, because this 

 continuous line of germinal potentiality has a genera- 

 tion longer span in him than in his parents. 



From the point of view of genetics, then, the real 

 mission of the somatoplasm, which is so marvelously 

 differentiated into all the various forms that we call 

 animals and plants, is simply to serve as a temporary 

 domicile for the immortal germplasm. Thus the parent 

 becomes as it were the "trustee of the germplasm," 

 but not the producer of the offspring, for the soma is 

 after all only the mechanism through which a fertilized 

 egg produces in due time another fertilized egg. 



