24 GEOLOGY 



bat that these must have had a common parent, and 

 between horse and this (?) parent &c., &c., but the 

 common parent may possibly have differed more 

 from either than the two do now from each other. 

 Now what evidence of this is there? So perfect 

 gradation in some departments, that some naturalists 

 have thought that in some large divisions, if all ex- 

 isting forms were collected, a near approach to perfect 

 gradation would be made. But such a notion is 

 preposterous with respect to all, but evidently so 

 with mammals. Other naturalists have thought 

 this would be so if all the specimens entombed in 

 the strata were collected 1 . I conceive there is no 

 probability whatever of this ; nevertheless it is certain 

 all the numerous fossil forms fall in(to), as Buckland 

 remarks, not present classes, families and genera, 

 they fall between them : so is it with new discoveries 

 of existing forms. Most ancient fossils, that is most 

 separated (by) space of time, are most apt to fall be- 

 tween the classes (but organisms from those coun- 

 tries most separated by space also fall between the 

 classes (e.g.) Ornithorhyncus ?). As far as geological 

 discoveries (go) they tend towards such gradation 2 . 

 Illustrate it with net. Toxodon, tibia and fibula,- 

 dog and otter, but so utterly improbable is (it), 

 in ex. gr. Pachydermata, to compose series as per- 

 fect as cattle, that if, as many geologists seem to 



1 The absence of intermediate forms between living organisms (and also 

 as regards fossils) is discussed in the Origin, Ed. i. pp. 279, 280, vi. p. 413. 

 In the above discussion there is no evidence that the author felt this difficulty 

 so strongly as it is expressed in the Origin, Ed. i. p. 299, as perhaps "the 

 most obvious and gravest objection that can be urged against my theory." 

 But in a rough summary written on the back of the penultimate page of 

 the MS. he refers to the geological evidence : " Evidence, as far as it does 

 go, is favourable, exceedingly incomplete, greatest difficulty on this theory. 

 I am convinced not insuperable." Buckland's remarks are given in the 

 Origin, Ed. i. p. 329, vi. p. 471. 



' That the evidence of geology, as far as it goes, is favourable to the 

 theory of descent is claimed in the Origin, Ed. i. pp. 343 345, vi. pp. 490 

 492. For the reference to net in the following sentence, see Note 1, p. 48, 

 of this Essay. 



