36 Charles Robert Darwin. 



making it more perfect and with every stroke confirming 

 his opinions. Thus, for example, Professor Agassiz pro- 

 duced no greater work than his "Essay on Classification." 

 You know that he was strenuously opposed to Darwin's 

 theory. But his Essay on Classification was unwittingly 

 an argument in its behalf. Mr. John Fiske informs us 

 that it was convincing to him of organic evolution before 

 Darwin's book appeared. But let us see how it is that a 

 system of classification is an argument for organic evolu- 

 tion. 



The classification of plants and animals has occupied the 

 scientific mind for many centuries. The earliest classifica- 

 tions were all popular and semi-popular ; that is to say, they 

 were based upon external resemblances. A whale was 

 called a fish because it had the general form and habits of 

 a fish. Even the great Buffon questioned whether a croc- 

 odile should not be classified as an insect because the hard- 

 ness of its casing corresponds to the hardness of a beetle's. 

 He finally decided that the crocodile is not an insect, and 

 for this reason : the crocodile is so large an animal that it 

 would make "altogether too terrible an insect" ! 



The endless confusion growing out of such a superficial 

 method suggested to Linnaeus that internal structure rather 

 than external appearance should be made the basis of class- 

 ification. At once the sky began to clear. A natural sys- 

 tem was worked out. It proved to be a tree-like system. 

 A short trunk represents the lowest organisms, concerning 

 which, when challenged, " Vegetable or Animal ? " we can- 

 not say. This trunk soon separates into two great branches, 

 one for the animal, the other for the vegetable, kingdom. 

 Smaller branches springing from these represent classes; 

 smaller from these, families ; then orders, genera, and 

 species bring us to the smallest branches, twigs, and leaves. 

 Now, in this tree-like system we have just such a system 

 as the evolutionist would naturally expect. It is " as clear 

 an expression as anything could be of the fact that all 

 species are bound together by the ties of genetic relation- 

 ship." Work it backward or forward and we get the same 

 impression : forward, the gradual shading off of characters 

 into forms more and more specialized is eloquent for the 

 fact of transmutation; backward, the difficulty of deter- 

 mining the genus, order, class, of certain organisms of the 

 humblest grades is most instructive. Proof there may not 



