Darwin and Descent 189 
Putting the three preceding passages together, we natur- 
ally inferred that “ the theory of natural selection” and 
“the principle of descent ” were the same things. We 
knew Mr. Darwin claimed the first, and therefore unhesita- 
tingly gave him the second at the same time. 
Again :— 
“Let us see how far these several facts and inferences 
accord with the theory of descent with modification” (p. 331) 
Again :— 
“Thus, on the theory of descent with modification, the 
main facts with regard to the mutual affinities of the extinct 
forms of life to each other and to living forms, seem to me 
explained in a satisfactory manner. And they are wholly 
inexplicable on any other view” (p. 333). 
The words “‘ seem to me ” involve a claim in the absence 
of so much as a hint in any part of the book concerning 
indebtedness to earlier writers. 
Again :— 
“ On the theory of descent, the full meaning of the fossil 
remains,” &c. (p. 336). 
In the following paragraph we read :— 
“But in one particular sense the more recent forms 
must, on my theory, be higher than the more ancient.” 
Again :— 
* Agassiz insists that ancient animals resemble to a 
certain extent the embryos of recent animals of the same 
classes ; or that the geological succession of extinct forms 
is in some degree parallel to the embryological development 
of recent forms. ... This doctrine of Agassiz accords 
well with the theory of natural selection ”’ (p. 338). 
“The theory of natural selection’’ became “ our 
theory” in 1869. The opinion of Agassiz accords excel- 
lently with the theory of descent with modification, but 
it is not easy to see how it bears upon the fact that lucky 
races are preserved in the struggle for life—which, according 
ity 
