BIOLOGICAL EVOLUTION 69 



has taken on new life and in his earlier writings and with most of 



his disciples it has become the " Allmacht " in the explanation of 



the formation of new species. 



Weismann's contributions to biology are thus summarized by 



Kellogg: 



His careful investigation and illumination of the vexed question of the 

 inheritance of acquired characters, his definite exposition of that point of 

 view which distinguishes sharply in the individual between the germ-plasm 

 (that particular protoplasm in the body from which the germ-cells, eventu- 

 ally new individuals, arise) and the soma-plasm (that which develops into, 

 or gives rise to, the rest of the body), his development of the interesting and 

 suggestive combinations of fact and theory designated by the phrase names 

 " continuity of the germ-plasm " and " immortality of the Infusoria," — 

 these products of his investigating and philosophizing mind prove him one 

 of the ablest of modern biological scholars. 1 



Of almost equal importance with the above for sociology is his 

 emphasis on the species as the unit in the struggle for existence, 

 for from this point of view sympathy, mutual aid and all forms of 

 co-operation that make for group strength are seen to be of adap- 

 tive value. 



Weismann's theory of " germinal selection " is also worthy of 

 note for although not widely accepted today we find in it an 

 application of the doctrine of adaptation to the determinants — 

 the theoretical sub-divisions of the germ-cell. Weismann holds 

 that these determinants compete for the possession of food and 

 that the successful dominate in the organism that is to be. 2 



Weismann's influence on social theory will be noted in succeed- 

 ing chapters; here it will suffice to bring out his teaching con- 

 cerning the continuity of the germ-plasm for the wide-spread 

 acceptance of this has led to the corresponding disbelief in the 

 inheritance of acquired characters as taught by Lamarck and 

 Spencer, and has been a most potent factor in the modern eugenics 

 movement. Weismann's statement of the theory is as follows: 



Heredity depends upon the fact that a small portion of the effective sub- 

 stance of the germ, the germ-plasm, remains unchanged during the develop- 

 ment of the ovum into an organism, and this part of the germ-plasm serves 

 as a foundation from which the germ-cells of the new organism are produced. 

 There is therefore continuity of the germ-plasm from one generation to 



1 Darwinism To-day, p. 188. 



2 For explanation of germinal selection, see Kellogg, op. cit., pp. 195 f. 



