16 HEREDITY 



from germ cell to germ cell, and that the body cells in 

 each generation are regarded as an offshoot, and as 

 having no function in reproduction beyond that of 

 guarding and nourishing the germ cells. 



The process of the setting apart of the germ cells at 

 the commencement of development is not an imaginary 

 one. In several instances it has been clearly distin- 

 guished under the microscope. 



To endeavour to make this clearer, we may imagine 

 a potter at work. He has a mass of clay ready kneaded 

 by his helper, and from this he cuts off a piece sufficient 

 for a vase. He moulds his vase, which is dried and 

 burnt in the kiln, and can never be turned back into 

 the original soft, plastic clay. But meantime his helper 



B 



has been at work increasing the size of the original 

 lump, so that he can immediately proceed to make 

 another vase from it. The lump of clay, ever growing, 

 ever about the same in character, is the germ plasm. 

 The vases, which we can suppose to be turned out on 

 the same pattern, are the successive generations. Only 

 to make our metaphor complete, the lump of clay would 

 require to be placed inside the developing vase, and to 

 grow there. Besides, of course, the whole process goes 

 on of itself. 



The consequences of this theory are far-reaching. 

 The connection between the characters of one genera- 

 tion and those of the next is not direct, but indirect. 

 The son's characteristics do not depend directly on 

 the father's, but indirectly in the sense that both depend 



