102 MR. DARWIN'S WORK AND 



perfectly competent to give rise to all the phenomena 

 which are exhibited by RACES in nature. Furthermore, 

 I believe that they are quite competent to account for all 

 that we may call purely structural phenomena which are 

 exhibited by SPECIES in nature. On that point also I have 

 already enlarged somewhat. Again, I think that the 

 causes assumed are competent to account for most of the 

 physiological characteristics of species, and I not only 

 think that they are competent to account for them, but 

 I think that they account for many things which other- 

 wise remain wholly unaccountable and inexplicable, and 

 I may say incomprehensible. For a full exposition of the 

 grounds on which this conviction is based, I must refer 

 you to Mr. Darwin's work ; all that I can do now is to 

 illustrate what I have said by two or three cases taken 

 almost at random. 



I drew your attention, on a previous evening, to the 

 facts which are embodied in our systems of Classification, 

 which are the results of the examination and comparison 

 of the different members of the animal kingdom one with 

 another. I mentioned that the whole of the animal 

 kingdom is divisible into five sub-kingdoms ; that each 

 of these sub-kingdoms is again divisible into provinces ; 

 that each province may be divided into classes, and the 

 classes into the successively smaller groups, orders, families, 

 genera, and species. 



Now, in each of these groups, the resemblance in structure 

 among the members of the group is closer in proportion 

 as the group is smaller. Thus, a man and a worm are 

 members of the animal kingdom in virtue of certain 

 apparently slight though really fundamental resemblances 

 which they present. But a man and a fish are members 

 of the same Sub-kingdom Vertebrata, because they are much 

 more like one another than either of them is to a worm, 

 or a snail, or any member of the other sub-kingdoms. For 

 similar reasons men and horses are arranged as members of 

 the same Class, Mammalia; men and apes as members 

 of the same Order, Primates ; and if there were any animals 

 more like men than they were like any of the apes, and yet 

 different from men in important and constant particulars 

 of their organization, we should rank them as members 

 of the same Family, or of the same Genus, but as of distinct 

 Spec -i 



That it is possible to arrange all the varied forms of 



