DISCOVE11Y BY MEANS OF INFERENCE. 603 



are so adapted to each other that from a few, or even a 

 single bone, could be inferred what the structure and 

 functions of all the other parts of the animal must have been. 



The great discoveries of Cuvier and St. Hilaire appear 

 to contradict each other, but the contradiction is only 

 apparent, and apparent contradiction is often a charac- 

 teristic of great truths in their early stages of develop- 

 ment, because such truths lie not on the surface of things, 

 but require considerable study and experience in order to 

 realise them. The apparent and the real are often the 

 opposite of each other. Von Baer (born in 1792), by 

 studying embryology, discovered, about the year 1828, by 

 observation, that the embryos of different species (as they 

 are termed) of living creatures are, in their earliest stages, 

 not perceptibly different from each other, except in size ; 

 also that they pass through the same order and appear- 

 ances of development, up to a certain point of time, and 

 then diverge, the point being different with each different 

 animal at which it begins to differentiate and show its 

 true kind ; and that with different species the order of 

 change is, fish, reptile, bird, mammal man having to pass 

 through all the stages of embryological development of 

 which other species of animals pass through only a portion 

 and he was thus enabled to discover, by fact and in- 

 ference, that the hypothesis of Lamarck and St. Hiliare 

 was a true one, and that all animals are formed upon one 

 great general plan. 



The results of the labour and study of these four 

 great naturalists prepared the way for the still wider 

 inferences of Darwin. Charles Darwin, the author of 

 the theory of natural selection, describes, in the follow- 

 ing words, the manner in which he was led to make that 

 discovery : ' In South America, three classes of facts 

 were brought strongly before my mind. Firstly, the 



