darwjn's theory of pangenesis. 97 



part of its parent. We know that it is a peculiarity 

 of bioplasm to divide and subdivide itself. By a 

 marvellous law of growth, the divided portions, when 

 properly nourished, increase in size, and acquire all 

 the qualities of their parent. A minute particle or 

 gemmule thrown off from a single mass of homo- 

 geneous bioplasm grows according to the laws which 

 belong to its parent, and becomes a mass like that 

 from which it dropped off. Physical identity be- 

 tween the parent and the child is the groundwork 

 of the explanation of the physical side of the law of 

 heredity in sameness. 



But now suppose that this animalcule, instead of 

 being a single mass of bioplasm, consists of a more 

 or less intricate structure. Let it be assumed that 

 the upper and lower side differ, and that each of these 

 has qualities distinct from those of the middle portion. 

 If you are to account for the reproduction of that 

 triplicate animal, you, according to Darwin's theory 

 of pangenesis, must suppose a small mass of bioplasm 

 thrown off from the lower section, another from the 

 middle part, and another from the upper. Call the 

 three portions of the animal 1, 2, and 3, and the gem- 

 mules thrown off from these parts respectively A, B, 

 and C [illustrating on blackboard]. A will have the 

 qualities of the portion of the animal from which it 

 comes; that is, of 1. B will possess the qualities of 

 2, and C of 3. 



You have, in this crucial case of hereditary descent, 

 the law of identity of substance in parent and gem- 

 mule carried out in a threefold manner. There is 



