5 1 2 Affinities of the feathered Race, 



I have found it to be a very general opinion among natu- 

 ralists,' that specific diversity must of necessity be accompanied 

 by some perceptible difference in the structure. To this I 

 cannot accede, until I hear of a sufficient reason why it 

 should be the case. We perceive every grade of approximation, 

 till in the shrews, for instance, a slight diversity in the form 

 of one of the back teeth comprehends all the difference. It 

 is 'therefore presumed that, as so very trivial a deviation 

 cannot be said to affect the animal's habits, for what purpose, 

 then, does it exist, save to intimate the separateness of the 

 species ? But, surely, it will not be contended that species 

 were created with a view that man should be able to distin- 

 guish them ! Surely, differences were not imposed merely to 

 facilitate the progress of human knowledge ! Is it not much 

 more rational to conclude, that, as great differences in the 

 structure import corresponding diversities in habit, so, by 

 the same rule, minor differences also imply an equivalent 

 diversity in degree ? Let us, again, consider the American and 

 European crows : here it would seem that specific diversity is 

 unaccompanied by any structural deviation. 



Of course, it is hardly necessary to hint the importance of 

 these facts to geological enquirers : they intimate the excessive 

 caution requisite ere we can venture to identify the fragments 

 of an organism, when even existing species, in many instances, 

 are not, probably, to be told apart. It must be admitted that 

 they warrant a good deal of scepticism as to many of the 

 identifications that have been assumed.* 



But to return now to the four typical genera, which have 

 led to the above lengthy digression. I certainly do not con- 

 ceive it necessary that there should be, in all instances, an 

 unbroken gradation into the subordinate forms, similar to 

 that from ifeferula into Philomela ; for it is evident that the 

 affinities of Philomela, and its relations to the thrush genus, 

 would be the same, were there no intervening examples. Still 

 it is reasonable to suppose that, generally speaking, such 

 series would occur; not, however, for the mere abstract 

 purposes of arrangement, but because there are grades in 

 localities and modes of life. That there should be species 

 variously modified upon any particular plan of structure, and 

 that the deviation should be greater in one instance than in 

 another, of course implies radiation from a general centre ; 



states, in one of his first letters, that black game was formerly abundant 

 in the neighbourhood, but that only one solitary grey-hen had been seen 

 for many years : such an individual might be expected to breed with a cock 

 pheasant. 



* For some facts bearing upon this subject, see Art. VII. — Ed. 



