120 THE THEORIES OF EVOLUTION 



differentiated. The formation of new gemmules 

 continues almost through the whole life of the cell 

 and may begin again under certain circumstances 

 after differentiation has become complete, for in- 

 stance whenever the cell undergoes some physiological 

 or pathological modification. 



While the gemmules are multiplying within the 

 cells, all the cells of the body send some of their gem- 

 mules to the sexual cells. This is done not only by 

 the definitely fixed cells of the adult organism, but 

 by all the ephemeral cells which appear during onto- 

 genesis and then disappear. The same happens 

 whenever the adult cells undergo a certain change. 

 The sexual product contains therefore in the shape 

 of gemmules all the anatomical and physiological 

 characters of the cells which it represents. 



Gemmules remain dormant in the ovum as long as 

 it does not develop, but as soon as the cleavage begins, 

 they distribute themselves among all the daughter- 

 cells at every stage of development and, owing to a 

 certain force of attraction, they finally reach the very 

 cells for which they are intended. They give life to 

 them and, through them, they fecundate the whole or- 

 ganism. Hence the name of pangenesis. To each 

 cell, the gemmules impart a character identical to that 

 of the cell from which they issued at the very moment 

 when the cell released them and dispatched them to- 

 wards the sexual organs. 



