GEOLOGY 23 



and showed signs of common descent, and yet were 

 created distinct. As long- as it was thought im- 

 possible that organisms should vary, or should any- 

 how become adapted to other organisms in a com- 

 plicated manner, and yet be separated from them by 

 an impassable barrier of sterility 1 , it was justifiable, 

 even with some appearance in favour of a common 

 descent, to admit distinct creation according to the 

 will of an Omniscient Creator ; or, for it is the same 

 thing, to say with Whewell that the beginnings of all 

 things surpass the comprehension of man. In the 

 former sections I have endeavoured to show that 

 such variation or specification is not impossible, nay, 

 in many points of view is absolutely probable. What 

 then is the evidence in favour of it and what the 

 evidence against it. With our imperfect knowledge 

 of past ages [surely there will be some] it would be 

 strange if the imperfection did not create some 

 unfavourable evidence. 



Give sketch of the Past, beginning with facts 

 appearing hostile under present knowledge, then 

 proceed to geograph. distribution, order of appear- 

 ance, affinities, morphology &c., &c. 



Our theory requires a very gradual introduction 

 of new forms 2 , and extermination of the old (to 

 which we shall revert). The extermination of old 

 may sometimes be rapid, but never the introduction. 

 In the groups descended from common parent, our 

 theory requires a perfect gradation not differing more 

 than breed(s) of cattle, or potatoes, or cabbages in 

 forms. I do not mean that a graduated series of 

 animals must have existed, intermediate between 

 horse, mouse, tapir^, elephant [or fowl and peacock], 



1 A similar passage occurs in the conclusion of the Origin, Ed. i. p. 481, 

 vi. p. 659. 



a See Origin, Ed. i. p. 312, vi. p. 453. 



3 See Origin, Ed. i. pp. 280, 281, vi. p. 414. The author uses his 

 experience of pigeons for examples for what he means by intermediate ; the 

 instance of the horse and tapir also occurs. 



( 



