Weismann s theory of Heredity (1891). 69 



It is, indeed, impossible not to admire the candour 

 of these admissions, or to avoid recognizing the truly 

 scientific spirit which they betoken. But, at the same 

 time, one is led to doubt whether in making them 

 Professor Weismann has sufficiently considered their 

 full import. He appears to deem it of comparatively 

 little importance whether or not acquired characters 

 can sometimes and in some degrees influence the 

 hereditary qualities of germ-plasm, provided he can 

 show that much the larger part of the phenomena of 

 heredity must be ascribed to the continuity of germ- 

 plasm. In other words, he seems to think that it 

 matters but little whether in the course of organic 

 evolution the Lamarckian factors have played but 

 a very subordinate part, or whether they have not 

 played any part at all. Moreover, I have heard one 

 or two prominent followers of Weismann give public 

 expression to the same opinion. Therefore I must 

 repeat that it makes a literally immeasurable difference 

 whether we suppose, with Galton, that the Lamarckian 

 factors may sometimes and in some degrees assert 

 themselves, or whether we suppose, with the great 

 bulk of Weismann 's writings and in accordance with 

 the logical requirements of his theory, that they can 

 never possibly occur in any degree. The distinctive 

 postulate of his theory of heredity, and one of the 

 two fundamental doctrines on which he founds his 

 further theory of evolution, is, that the physiology of 

 sexual reproduction cannot admit of any inversion of 

 the relations between "germ-plasm " and " somatic idio- 

 plasm V This is a perfectly intelligible postulate, but 

 it is not one with which we may play fast and loose. 



1 See for example, Essays, p. 229. 



