106 HEREDITY. 



narrow receptacles. They cannot be absolutely in- 

 finite in numbers, however, for if so they could not 

 be nourished. Darwin himself says that " excessive- 

 ly minute and numerous as the gemmules are believed 

 to be, an infinite number derived, during a long course 

 of modification and descent, from each unit of each 

 progenitor, could not be supported or nourished by 

 the organism." (Animals and Plants under Domesti- 

 cation, vol. ii. chap, x.,' American edition, p. 396.) 

 Nevertheless they are so small as to be wholly invisi- 

 ble to the microscope. That is an important point, 

 for it makes the theory one which it is very difficult to 

 disprove. The gemmules are objects of the imagina- 

 tion. How are we to disprove their existence ? You 

 may imagine the gemmules floating in the blood, and 

 permeating tissues which the blood cannot penetrate. 

 If you are of those who establish their theories by 

 supposing that what cannot be disproved is proved, 

 then you may prove the existence of these gemmules. 

 Nobody can easily disprove the existence of physical 

 masses which the best microscope cannot perceive. 

 It is all a matter of imagination the existence of 

 the gemmules ; and will be, probably, for ages and 

 ages yet, for no microscope pretends to see any thing 

 as small as these gemmules must be. 



One thing, however, we do know, that, if the pan- 

 genetic gemmules are inconceivably small, they must 

 pass everywhere through the living tissues. They 

 easily permeate cell-walls. Therefore, in the vege- 

 table kingdom, when the gemmules pass freely from 

 cell to cell, we should suppose that a bud borne 



