xiu EXTENSIONS OF DARWINISM 271 



Germinal Selection 



The numerous and varied phenomena which have been 

 merely sketched in outline in the present chapter receive an 

 approximate explanation by Professor Weismann's theory of 

 germinal selection, which he first published in 1896. He 

 appears to have been led to it by feeling the difficulty of 

 explaining many of these phenomena by the "natural 

 selection " of Darwin ; but to have laid more stress on those 

 of Section 2 of the present chapter than those of Section 3. 

 He had in 1892 published his elaborate volume on The 

 Germ -Plasm a Theory of Heredity, to which this later 

 theory is a logical sequel. 



During the last quarter of a century many striking 

 discoveries have been made in what may be termed the 

 mechanism of growth and reproduction ; each successive 

 advance in microscopic power and methods of observation 

 have brought to light whole worlds of complex structure 

 and purposive transformations in what was before looked 

 upon as structureless cells or corpuscles. Some attempt will 

 be made in a later chapter to discuss these primary life- 

 phenomena ; here it is only necessary to show briefly how 

 Weismann's new theory helps us to understand the facts of 

 life -development we have been dealing with. For this 

 purpose I cannot do better than quote Professor Lloyd 

 Morgan's very clear statement of the theory. He says : * 



" The additional factor which Dr. Weismann suggests is what 

 he terms ' germinal selection.' This, briefly stated, is as follows : 

 There is a competition for nutriment among those parts of the germ 

 named determinants, from which the several organs or groups of 

 organs are developed. In this competition the stronger deter- 

 minants get the best of it, and are further developed at the expense 

 of the weaker determinants, which are starved, and tend to dwindle 

 and eventually disappear. The suggestion is interesting, but one 

 wellnigh impossible to test by observation. If accepted as a factor, 

 it would serve to account for the inordinate growth of certain 

 structures, such as the exuberance of some secondary sexual 

 characters, and for the existence of determinate variations, that is 

 to say, variations along special or particular lines of adaptation." 



It may be well to give here Weismann's own definition 

 1 Habit and Instinct, p. 310. 



