266 THE GENESIS OF SPECIES. [CHAP. 



importance, all point to such a mode of specific mani- 

 festation. 



One very good illustration has been adduced by Pro- 

 fessor Flower in the introductory lecture of his first 

 Hunterian Course. 1 It is the reduction in size, to a greater 

 or less degree, of the second and third digits of the foot 

 in Australian marsupials, and this, notwithstanding the 

 very different form and function of the foot in different 

 groups of those animals. 



A similarly significant evidence of relationship is afforded 

 by processes of the zygomatic region of the skull in certain 

 edentates existing and extinct. 



Again, the relation between existing and recent faunas 

 of the different regions of the world, and the fact that the 

 progress in organization has been for the most part from 

 the more general to the more special, tend to support the 

 doctrine of evolution. 



Almost all the facts brought forward by the patient 

 industry of Mr. Darwin in support of his theory of 

 " Natural Selection " are of course available as evidence 

 in favour of the agency of pre-existing and similar 

 animals in specific evolution. 



Now the new forms must be produced by changes taking 

 place in organisms at, after, or before their birth, either in 

 their embryonic or towards or in their adult condition. 



Examples of strange births are sufficiently numerous, 

 and they may arise either from direct embryonic modifica- 

 tions or apparently from some obscure change in the 

 parental action. To the former category belong the hosts 

 of instances of malformation through arrest of develop- 



1 Introductory Lecture of February 14, 1870, pp. 2430, Figs. 14. 

 (Churchill and Sons.) 



