CHAPTER II. 



CLASSIFICATION. 



THE first line of direct evidence in favour of organic 

 evolution which I shall open is that which may be 

 termed the argument from Classification. 



It is a matter of observable fact that different forms 

 of plants and animals present among themselves more 

 or less pronounced resemblances. From the earliest 

 times, therefore, it has been the aim of philosophical 

 naturalists to classify plants and animals in accord- 

 ance with these resemblances. Of course the earliest 

 attempts at such classification were extremely crude. 

 The oldest of these attempts with which we are ac- 

 quainted- namely, that which is presented in the books 

 of Genesis and Leviticus arranges the whole vegetable 

 kingdom in three simple divisions of Grass, Herbs, and 

 Trees ; while the animal kingdom is arranged with 

 almost equal simplicity with reference, first to habitats 

 in water, earth, or air, and next as to modes of pro- 

 gression. These, of course, were what may be termed 

 common-sense classifications, having reference merely 

 to external appearances and habits of life. But when 

 Aristotle laboriously investigated the comparative 

 anatomy of animals, he could not fail to perceive that 

 their entire structures had to be taken into account in 



