THE PHENOMENA OF ORGANIC NATURE, 139 



logical 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 Classifi- 

 cation, which are the results of the examination and 

 comparison of the difi"erent 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 succes- 

 sively 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 



