SOME ASPECTS OF ZOOLOGY 47 



Weismann by his much more fully worked out theory of the 

 Continuity of the Germ Plasm, who gave us some real insight 

 into this question. 



The substance of the " egg " i.e. the united male and 

 female germ-cells by growth and division expands into the 

 individual, whose body is subject to all sorts of external in- 

 fluences from birth onwards and therefore exhibits individual 

 variation within the limits illustrated by Johannsen's beans. 

 But a portion of the whole, namely the germ-plasm, is set 

 aside for reproduction. Sheltered within the individual's 

 body, it is not exposed to the influence of the environment and 

 remains unaltered (I will not say unalterable), and forms the 

 material for the new generation. On this conception, which 

 undoubtedly contains many elements of truth, the germ- 

 plasm is continuous from generation to generation and practi- 

 cally is the race, with all its peculiarities and potentialities. 

 The individuals, whose bodies are a by-product, as it were, 

 of the germ-plasm, are the frail and perishing beings alluded 

 to by Harvey. Their bodies are said to be composed of 

 perishable somatoplasm, in contrast to the potentially im- 

 perishable germ-plasm. 



It follows from this conception that the deviations from 

 the mean, the changes, induced in individuals by the incidence 

 of external agents, do not affect the germ-plasm, and therefore 

 are not inherited. 



The individual is relatively of no importance ; the race is 

 everything. 



A critical analysis of all the available evidence has shown 

 no authentic instance of the inheritance of changes of structure 

 or habit which were acquired by an individual during his (or 

 her) lifetime, and were distinctly " somatogenic," that is to 

 say, affected only the somatoplasm of the individual in 

 question. 



In my opinion, as in that of most biologists, the proposi- 

 tion that somatogenic variations are not inheritable is as 

 firmly established as any in natural science. 



The moral and ethical deductions from this proposition are 

 profoundly important, and must be taken fully into account 



