THE HYPOTHESIS OF PANGENESIS 125 



tions when the germ-cell itself undergoes development 

 and becomes a mature individual. 



Thus the gemmules stored up in the germ-cells of 

 Diagram / represent a previous generation of body- 

 cells, while those crossing the space separating body- 

 from germ-cells represent the existing generation. 



Nor is this all ; for we are also compelled to believe 

 that gemmules from the cells of large numbers of genera- 

 tions of ancestors are present in many germ-cells, 

 accounting for the facts of atavism or ' throwing back '. 

 When an animal ' throws back ' to some remote ancestor, 

 the gemmules must have been handed down in a dormant 

 condition through all intermediate generations. 



Furthermore, there are grave practical difficulties in 

 the way of the acceptance of Darwin's hypothesis. If it 

 were true, we should expect that mutilations, especially 

 such as are inflicted early in life, would be transmitted 

 to offspring; for all the cell-generations later than the 

 date of the injury would be absent, and therefore unrepre- 

 sented by gemmules. But there is no evidence in favour 

 of the transmission of mutilations, however early they 

 may be inflicted. All the evidence, when carefully 

 examined, points in the opposite direction. 



Again, in the process of transfusion, when the blood 

 of one individual is replaced by that of another, it seems 

 reasonable to suppose that, if the gemmules exist, many 

 of them would be carried over, and would collect in the 

 germ-cells of the individual which received the blood, 

 and that thus some characters of one individual would 

 afterwards appear in the offspring of another. Careful 

 experiments, conducted by Galton and later by Romanes, 

 prove that such transference of hereditary characters does 

 not accompany the transfusion of blood. 



Not only may blood be transfused, but various tissues 

 may be grafted and will thrive on another individual of 

 the same species l . In these cases, too, we should expect 

 that such transferred tissues would produce effects upon 



1 Grafted tissues will also thrive on an individual of a very different 

 species ; but such an experiment, however interesting from other points 

 of view, would obviously be unsuitable as a test of Pangenesis. 



