Summary 



In summing up the evidence as to the heritabiUty or 

 non-heritabiUty of acquired characters, we may state the 

 present position as follows : 



1. The heritable characters are transmitted through 

 the germ plasm (sperms and eggs) which is contin- 

 uous from generation to generation and which is not 

 produced by the body (soma). (See page 54). 



2. No mechanism exists, as far as is known, whereby a . 

 structural change in a part of the body influences 

 the germ plasm in such a way that the offspring 

 shows the same modification. 



3. All so-called instances of inherited acquired char- 

 racters are based either on a mis-understanding of 

 the exact nature of such characters or on loose meth- 

 ods of reasoning. None have satisfactorily met the 

 test of rigid experimental proof (See page 60). 



4. The persistence of the chromosomes and Mende- 

 lian factors is wholly opposed to the idea that the 

 body influences specifically the germ plasm. (See 

 chapter 16). 



It is evident that the subject has not been an easy one 

 to settle, when one rembers that such eminent men as Lam- 

 arck, Herbert Spencer, Haeckel, Hertwig, Cope, Hyatt and 

 Sir W. Turner have been advocates of the theory of the in- 

 heritance of acquired characters; while opposed to the the- 

 ory have been Darwin, Wallace, Galton, Huxley, Ray Lan- 

 kester, Weismann and His. 



Chapter 11— DE VRIES' MUTATION THEORY (1901) 



We have already noted (page 20) that one of the objec- 

 tions to the full acceptance of Darwin's Theory of Natural 

 Selection as an interpretation of the mode of evolution was 

 the great length of time it demanded for the development of 

 new species, not to speak of genera, families and classes, of 

 plants and animals. The theory practically removed the 

 problem of evolution beyond the range of experimental in- 

 vestigation or proof. Such an unscientific attitude did not 

 appeal to many critics, and a few resolved to find out by ob- 

 servation and experiment if new forms might not possibly 

 originate in a much shorter time than that demanded by 

 Darwin's theory. 



Already investigators had evidence that new forms had 

 occasionally arisen suddenly as sports, and St. Hilaire, a 



64 



