24 PROBLEMS OF EVOLUTION 



theses and supplementary hypotheses must be reckoned among 

 the most serious ills that a biologist at the present day is heir to. 

 Moreover, he seems sometimes through carelessness of expres- 

 sion to deify Natural Selection and endow it with creative power. 

 But careful reading of his essays will remove this first im- 

 pression, though, short of actually creating, he assumes that it 

 can do anything and everything. 



What solid result is there ? That is the important question. 

 An impartial critic must own, that from all Weismann's theoris- 

 ing there emerges one great idea of the utmost value as a basis 

 for a theory of heredity the continuity of the germ-plasm. 

 This doctrine once established, the non-inheritance of the modi- 

 fications of the soma due to exercise or external conditions, 

 though not a logical deduction from.it, yet becomes a proba- 

 bility. Round the question of heredity there still rages a 

 turmoil of angry controversy, but, though the clamour does 

 not diminish, there is less divergence of view. The rival 

 theories tend to approximate to Weismann's and, in spite of 

 all the strife and hurly-burly, the continuity of the germ-plasm 

 holds the field. 



The theory rests on a firm foundation. We know that the 

 nucleus of the germ cells contain closely packed, all the char- 

 acters of the animal that is to grow from them. If part of the 

 germ-plasm remains undisintegrated, its architecture unshattered ; 

 if the germ cells are separated off from the rest of the body 

 (from the soma) except in so far as they receive nourishment 

 from it ; if in their seclusion they continue to multiply by fission, 

 each resultant half containing the same characters, all else in 

 their life being merely the assimilation of food then we can 

 understand how parental and distant ancestral traits can be 

 transmitted. But if the particles that represent characters were 

 scattered all over the body, how could they be re-collected and 

 replaced each in its proper position ? Such a thing would 

 puzzle the wildest imagination. We are driven, then, to con- 

 clude that germ-plasm is kept unaltered and that from it springs 

 the next generation. 



Besides this we have a parallel among the Protozoa. They 



