166 THE CONTINUITY OF THE GERM-PLASM AS THE 



part of the problem which is here placed in the foreground, viz. 

 the explanation of the fact that the tendencies of heredity are 

 present in single cells, but it is rather concerned with the question 

 as to the manner in which it is possible to conceive the trans- 

 mission of a certain tendency of development into the sexual cell, 

 and ultimately into the organism arising from it. The same may 

 be said of the hypothesis of His 1 , who, like Hackel, regards heredity 

 as the transmission of certain kinds of motion. On the other hand, 

 it must be conceded that Darwin's hypothesis goes to the very root 

 of the question, but he is content to give, as it were, a provisional 

 or purely formal solution, which, as he himself says, does not claim 

 to afford insight into the real phenomena, but only to give us 

 the opportunity of looking at all the facts of heredity from a 

 common standpoint. It has achieved this end, and I believe it 

 has unconsciously done more, in that the thoroughly logical ap- 

 plication of its principles has shown that the real causes of 

 heredity cannot lie in the formation of gemmules or in any 

 allied phenomena. The improbabilities to which any such theory 

 would lead are so great that we can affirm with certainty 

 that its details cannot accord with existing facts. Further- 

 more, Brooks' 2 well-considered and brilliant attempt to modify 

 the theory of Pangenesis, cannot escape the reproach that it 

 is based upon possibilities, which one might certainly describe as 

 improbabilities. But although I am of opinion that the whole 

 foundation of the theory of Pangenesis, however it may be modified, 

 must be abandoned, I think, nevertheless, its author deserves 

 great credit, and that its production has been one of those indirect 

 roads along which science has been compelled to travel in order to 

 arrive at the truth. Pangenesis is a modern revival of the oldest 

 theory of heredity, that of Democritus, according to which the 

 sperm is secreted from all parts of the body of both sexes during 

 copulation, and is animated by a bodily force ; according to this 

 theory also, the sperm from each part of the body reproduces the 

 same part 3 . 



1 His, ' Unsre Korperform etc.,' Leipzig, 1875. 



8 Brooks, "The Law of Heredity,' Baltimore, 1883. 



3 Galton's experiments on transfusion in Rabbits have in the mean time really 

 proved that Darwin's gemmules do not exist. Roth indeed states that Darwin has 

 never maintained that his gemmules make use of the circulation as a medium, but 

 while on the one hand it cannot be shown why they should fail to take the 



