138 Darwin, and after Darwin. 



been absolutely continuous "since the first origin of 

 life." On the other hand, the doctrine of continuity 

 may be held in the widely different sense in which 

 it has been presented by Galton's theory of Stirp. 

 Here the doctrine is, that while for the most part 

 the phenomena of heredity are due to the continuity 

 of the substance of heredity through numberless 

 generations, this substance (" Stirp ") is nevertheless 

 not absolutely continuous, but may admit, in small 

 though cumulative degrees, of modification by use- 

 inheritance and other factors of the Lamarckian kind. 

 Now this all -important distinction between these two 

 theories of continuity has been fully explained and 

 thoroughly discussed in my Examination ; therefore 

 I will not here repeat myself further than to make 

 the following remarks. 



The Weismannian doctrine of continuity as abso- 

 lute (base-line of the diagram) is necessary for the 

 vast edifice of theories which he has raised upon it 

 (the Y), first as to the minute nature and exact 

 composition of the substance of heredity itself 

 (" Germ-plasm "), next as to the precise mechanism 

 of its action in producing the visible phenomena of 

 heredity, variation, and all allied phenomena, and, 

 lastly, the elaborate and ever-changing theory of 

 organic evolution which is either founded on or 

 interwoven with this vast system of hypothetic 

 speculation. Galton's doctrine of continuity, on 

 the other hand, is a " Theory of Heredity," and 

 a theory of heredity alone. It does not meddle 

 with any other matters whatsoever, and rigidly 

 avoids all speculation further than is necessary for 

 the bare statement and inductive support of the 



