INTRODUCTION I3 



heredity in his essay on 'Intracellular Pangenesis."* The 

 opinions there expressed really contradict the title of the paper ; 

 for pangenesis, in Darwin's sense, means the development of 

 gemmules throughout the body, — the composition of the heredi- 

 tary substance from gemmules which are derived from all the 

 cells of the body. This very point in Darwin's hypothesis is set 

 aside completely by de Vries : the most characteristic part of it 

 is removed, and what remains is of a more general nature, con- 

 sisting of principles which, in one form or another, must form 

 the basis of every theory of heredity, at the present day at any 

 rate. Some ideas of his own, however, are then added, and it 

 is these which give a characteristic stamp to his whole series of 

 conceptions. If we regard his hypothesis, as de Vries himself 

 does, as an alteration of the Darwinian theory of pangenesis, it 

 is certainly a radical one. and is of such a kind as at one stroke 

 to infuse new life into the latter, which had become untenable 

 in its original form. 



De Vries distinguishes two parts in Darwin's theory of pan- 

 genesis, one of which he rejects, while he retains the other. He 

 calls the former portion the ' transport hypothesis,' meaning 

 thereby the assumption of the origin of the gemmules in all the 

 cells of the body, their separation from the cells, circulation in 

 the blood, and ultimate aggregation in the germ-cells. And 

 relying on my rejection of the heredity of 'somatogenic' charac- 

 ters, he sho\vs that the assumption of the transportation of 

 the gemmules from all the cells of the body to the germ-cells 

 is superfluous. He thus does away with that portion of the 

 hypothesis of pangenesis w^hich makes it unacceptable to most 

 people, and places the theory on a new and firmer foundation 

 on which it is capable of further development. 



De Vries nevertheless goes too far if he looks upon the 

 • transport hypothesis ' as necessary only for explaining the 

 transmission of somatogenic qualities. It must not be for- 

 gotten that the idea of the continuity of the germ-plasm did not 

 exist in Darwin's time. How could the gemmules of all the 

 cells of an organism enter its germ-cells unless they are formed 

 in the body-cells, migrate therefrom, circulate through the body, 

 and come together in the germ-cells? A direct connection 

 between the fertilised egg-cell and the germ-cells of the organism 



* ' Die Intracelliilare Pangenesis,' Jena, 1889. 



