Author's Introduction 5 



It has always seemed to me that most authors have not 

 sufficiently distinguished these two aspects of the hy- 

 pothesis, and that their objections against accepting the 

 theory of transportation have misled them into over- 

 looking the paramount significance of the doctrine of 

 gemmules. 



To my mind Darwin's provisional hypothesis of pan- 

 genesis consists of the following two propositions : 



1. In every germ-cell (egg-cell, pollen-grain, bud, 

 etc.) the individual hereditary qualities of the whole or- 

 ganism are represented by definite material particles. 

 These multiply by division and are transmitted during 

 cell-division from the mother-cell to the daughter-cells. 



2. In addition, all the cells of the body, at different 

 stages of their development, throw off such particles; 

 these fiow into the germ-cells, and transmit to them the 

 qualities of the organism, which they are possibly lack- 

 ing. ( Transportation-hypothesis ) . 



The second assumption possessed, for Darwin himself, 

 only limited importance, in the case of plants and corals, 

 as he considered a transportation of gemmules from one 

 branch to another impossible. It does not apply to the 

 workers of ants and bees, nor to the double stocks (gilli- 

 fiower) mentioned several times by Darwin. These do 

 not possess any stamens and pistils themselves, and their 

 characteristics must therefore be transmitted from one 

 generation to the other through the fertile single specimens 

 of the race. The facts, for the explanation of which the 

 theory in question was brought forth, have gained neither 

 in number nor in trustworthiness during the twenty years 

 since the publication of Darwin's book. 



Doubts of its necessity, therefore, are quite permis- 

 sible, and it is the chief service of Weismann to have 



