Pangenesis 111 



which in fertilization again produces the most varied combinations 1 . 

 In this way all the cooperations which the carriers of hereditary 

 characters are capable of in a species are produced ; this must give 

 it an appreciable advantage in the struggle for life. 



The admirers of Charles Darwin must deeply regret that he did 

 not live to see the results achieved by the new Cytology. What 

 service would they have been to him in the presentation of his 

 hypothesis of Pangenesis ; what an outlook into the future would 

 they have given to his active mind ! 



The Darwinian hypothesis of Pangenesis rests on the conception 

 that all inheritable properties are represented in the cells by small 

 invisible particles or gemmules and that these gemmules increase by 

 division. Cytology began to develop on new lines some years after 

 the publication in 1868 of Charles Darwin's Provisional hypothesis 

 of Pangenesis 2 , and when he died in 1882 it was still in its infancy. 

 Darwin would have soon suggested the substitution of the nuclei 

 for his gemmules. At least the great majority of present-day 

 investigators in the domain of cytology have been led to the con- 

 clusion that the nucleus is the carrier of hereditary characters, and 

 they also believe that hereditary characters are represented in the 

 nucleus as distinct units. Such would be Darwin's gemmules, which in 

 conformity with the name of his hypothesis may be called pangens 3 : 

 these pangens multiply by division. All recently adopted views may 

 be thus linked on to this part of Darwin's hypothesis. It is otherwise 

 with Darwin's conception to which Pangenesis owes its name, namely 

 the view that all cells continually give off gemmules, which migrate 

 to other places in the organism, where they unite to form repro- 

 ductive cells. When Darwin foresaw this possibility, the continuity 

 of the germinal substance was still unknown 4 , a fact which excludes 

 a transference of gemmules. 



But even Charles Darwin's genius was confined within finite 

 boundaries by the state of science in his day. 



It is not my province to deal with other theories of development 

 which followed from Darwin's Pangenesis, or to discuss their histo- 

 logical probabilities. We can, however, affirm that Charles Darwin's 

 idea that invisible gemmules are the carriers of hereditary characters 

 and that they multiply by division has been removed from the 

 position of a provisional hypothesis to that of a well-founded theory. 

 It is supported by histology, and the results of experimental work in 

 heredity, which are now assuming extraordinary prominence, are in 

 close agreement with it. 



1 A. Weismann gave the impulse to these ideas in his theory on Amphimixis. 

 - Animals and Plants under Domestication, London, 1868, Chapter xxvii. 



3 So called by H. de Vries in 1889. 



4 Demonstrated by Nussbaum in 1880, by Sachs in 1882, and by Weismann in 1885. 



