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natural history of the two groups which technical 

 zoology has bufc emphasised in its turn. Yet the 

 scientific examination of these beings reveals bonds 

 of connexion between them, all unsuspected by the 

 ordinary reader, and demonstrates further, in the 

 most suggestive fashion, that the likeness to be pre- 

 sently alluded to must possess some origin and 

 meaning. That origin, evolution maintains, is 

 tf descent " from a common stock ; the meaning is 

 that seen throughout all similar series of likenesses, 

 namely, the natural result of the laws of animal 

 development. In the case of birds and reptiles, the 

 same considerations appeal to us which I have already 

 indicated as existent in the details of frog-develop- 

 ment. Either the likenesses science discovers between 

 apparently distinct groups of animals are explicable, 

 or they are not explicable. If the former, then 

 science declares, with unanimous voice, that the like- 

 nesses are due to common descent, as the unlikenesses 

 are due to the variations and modifications produced 

 during the evolution of the race. If, on the other 

 hand, the likenesses are inexplicable as I hold them 

 to be on any other theory save that of evolution 

 then must mankind fold their hands in the acknow- 

 ledgment of an ignorance that might legitimately, by 

 its avowal, close the door to astronomical research, to 

 geological work, and to scientific investigation of 

 every kind. 



I am led to make these remarks because several 

 correspondents of Knowledge have remarked to the 



