' THE ORIGIN OP SPECIES ' 99 



which flows from it almost as a mathematical necessity 

 when once suggested ; for, given indefinite variability, 

 and a geometrical rate of increase, it must needs 

 follow that some varieties will be better suited to the 

 circumstances than others, and therefore that they will 

 survive on the average in increased proportions. A 

 passage from one of Lyell's early letters will show how 

 near he too went to this great luminous generalisation, 

 and yet how utterly he missed the true implications of 

 his own vague and chaotic idea. He writes thus to Sir 

 John Herschel in 1836, while Darwin was still but 

 homeward bound on the voyage of the ' Beagle ' : 



' In regard to the origination of new species, I am 

 very glad to find that you think it probable that it may 

 be carried on through the intervention of intermediate 

 causes. ... An insect may be made in one of its 

 transformations to resemble a dead stick, or a leaf, or a 

 lichen, or a stone, so as to be somewhat less easily 

 found by its enemies; or if this would make it too 

 strong, an occasional variety of the species may have 

 this advantage conferred on it ; or if this would be still 

 too much, one sex of a certain variety. Probably there 

 is scarcely a dash of colour on the wing or body of 

 which the choice would be quite arbitrary, or which 

 might not affect its duration for thousands of years.' 



Now, this comes in some ways perilously near to 

 Darwin indeed ; but in the most important point of all 

 it is wide apart from him as the pole is from the 

 equator. For Lyell thought of all this as a matter of 

 external teleological arrangement ; he imagined a de- 

 liberate power from outside settling it all by design 

 beforehand, and granting to varieties or species these 



