The Tree of Evolution 35 



building conceal the foundations, so later anatomical 

 work, although it has only amplified and extended 

 Huxley's discoveries, has made them seem less striking 

 to the modern reader. The present writer, for instance, 

 learned all that he knows of anatomy in the last ten 

 years, and until he turned to it for the purpose of this 

 volume he had never referred to Huxley's original 

 paper. When he did so, he found from beginning to 

 end nothing that was new to him, nothing that was 

 strange : all the ideas in the memoir had passed into 

 the currency of knowledge and he had been taught 

 them as fundamental facts. It was only when he 

 turned to the text-books of anatomy and natural his- 

 tory current in Huxley's time that he was able to 

 realise how the conclusions of the young ship-surgeon 

 struck the Fellows and President of the Royal Society 

 as luminous and revolutionary ideas. 



In the first half of the century, a conception of the 

 animal kingdom prevailed which was entirely different 

 from our modern ideas. We know now that all animals 

 are bound together by the bond of a common descent, 

 and we seek in anatomy a clue to the degrees of relation- 

 ship existing among the different animals we know. We 

 regard the animal kingdom as a thicket of branches all 

 springing from a common root. Some of these spring 

 straight up from the common root unconnected with 

 their fellows. Others branch repeatedly, and all the 

 branches of the same stem have features in common. 

 What we see in the living world is only the surface of 

 the thicket, the tops of the twigs; and it is by examina- 

 tion of the structure of this surface that we reconstruct 

 in imagination the whole system of branches, and know 

 that certain twigs, from their likeness, meet each other 

 a little way down ; that others are connected only very 



