72 GENETICS 



lies within the body like a commensal or parasite. It 

 is hard to see, therefore, how a germ-cell can be 

 changed except in a general nutritive way which is 

 quite different from a change in character of any 

 hereditary significance. 



The somatoplasm is something that has traveled 

 out from the original fundamental germplasm along 

 the paths of differentiation and elaboration. The more 

 complex the body-cells become, that is, the more suc- 

 cessive modifications they undergo, the more difficult 

 it is for these somatic cells to return to their original 

 primitive germinal estate. 



In many lower forms of life where cell elaboration 

 is not so great, a part lost by amputation is often 

 regenerated, but this process is not possible in higher 

 forms where the parts represent cell complexes too 

 hopelessly differentiated to begin anew the unfolding 

 sequences of their elaboration. This difficulty was 

 a very real one in the mind of that famous nocturnal 

 inquirer Nicodemus when he asked: "How can a man 

 be born when he is old? Can he enter a second time 

 into his mother's womb and be born?" 



Not only the development of the race which we call 

 evolution, but also the determination of the individual 

 in heredity, is a chain of onward-moving sequences like 

 the succession of events in history. It is hard to see 

 how recent events can influence preceding events. It is 

 hard to see how the water that has gone over the dam 

 can return and affect the flow of the river upstream in 

 any direct way. It is likewise hard to see how differ- 

 entiated somatoplasm, which represents the end stage 



