348 PALAEONTOLOGY AND EVOLUTION xi 



foundation. So far, indeed, as the Invertcbrata and 

 the lower Vertebrata are concerned, the facts and 

 the conclusions which are to be drawn from them 

 appear to me to remain what they were. For 

 anything that, as yet, appears to the contrary, the 

 earliest known Marsupials may have been as 

 highly organised as their living congeners ; the 

 Permian lizards show no signs of inferiority to 

 those of the present day; the Labyrinthodonts 

 cannot be placed below the living Salamander and 

 Triton ; the Devonian Ganoids are closely related 

 to Polypterus and to Lepidosiren. 



But when we turn to the higher Vertebrata, 

 the results of recent investigations, however we 

 may sift and criticise them, seem to me to leave a 

 clear balance in favour of the doctrine of the 

 evolution of living forms one from another. 

 Nevertheless, in discussing this question, it is 

 very necessary to discriminate carefully between 

 the different kinds of evidence from fossil re- 

 mains which are brought forward in favour of 

 evolution. 



Every fossil which takes an intermediate place 

 between forms of life already known, may be said, 

 so far as it is intermediate, to be evidence in 

 favour of evolution, inasmuch as it shows a possible 

 road by which evolution may have taken place. 

 But the mere discovery of such a form does not, 

 in itself, prove that evolution took place by and 

 through it, nor does it constitute more than pre- 



