AND CLASSIFICATION. 23 



This is but the simplest illustration, taken 

 from the most familiar objects, of this compar- 

 ative method ; but the same process is equally 

 applicable to the most intricate problems in an- 

 imal structures, and will give us the clew to all 

 true affinities between animals. The education 

 of a naturalist now consists chiefly in learning 

 how to compare. If he have any power of 

 generalization, when he has collected his facts, 

 this habit of mental comparison will lead him 

 up to principles, and to the great laws of combi- 

 nation. It must not discourage us, that the pro- 

 cess is a slow and laborious one, and the results 

 of one lifetime after all very small. It might 

 seem invidious, were I to show here how small 

 is the sum total of the work accomplished even 

 by the great exceptional men, whose names are 

 known throughout the civilized world. But I 

 may at least be permitted to speak disparagingly 

 of my own efforts, and to sum up in the fewest 

 words the result of my life's work. I have de- 

 voted my whole life to the study of Nature, and 

 yet a single sentence may express all that I have 

 done. I have shown that there is a correspond- 

 ence between the succession of Fishes in geologi- 

 cal times and the different stages of their growth 

 in the egg, this is all. It chanced to be a 

 result that was found to apply to other groups 

 and has led to other conclusions of a like nature. 



