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. 
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.? 
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. 
