514? Affinities of the feathered Race, 



Before concluding this, I must call attention to another 

 point worthy of consideration. To recur again to the four 

 typical genera we have all along been considering, and which, 

 of course, it is most satisfactory to revert to in every instance, 

 it appears that the central species, for the most part, exhibit a 

 marked increase of size, being generally about the largest of 

 those framed on their respective plans of structure. I do not 

 say that this obtains in every instance, but still it is so general 

 as to be quite worthy of attention ; and the rationale of it 

 appears simply to be, that, as typical forms are more adapted 

 for general distribution, and better calculated for finding sub- 

 sistence in a variety of localities, than those modifications of 

 them which are organised expressly for peculiar places only, 

 we must infer that an increase of stature would, as a general 

 rule, be incompatible with the well-doing of aberrant races ; 

 or, to put it inversely, that beings of comparatively large 

 size require to be less partial in their adaptations ; that (their 

 wants being greater) they should not be too much confined 

 to particular places for the needful supply of food. However, 

 this is a rule so broken into by exceptions, and so entirely 

 dependent on the character of the particular adaptation, that, 

 though obvious enough in the main, it is much more likely 

 to meet with assent than demonstration. Certain it is, that, 

 in very many groups, the largest species are among the most 

 centrally typical. Witness, by way of example, the wood- 

 peckers and the parrots. 



In fabricating an arrangement according to the natural 

 method (i. e. based on the true affinities of species), we cannot 

 be too much impressed with the consideration that organisms 

 must be ever regarded in their totality; that no one structural 

 character can be expected to hold in all instances, however 

 important in particular cases. We have only to consider the 

 fact, that, in a natural group, it is but the same leading plan 

 of structure which is so variously modified, each organ, in its 

 turn, being adapted differently to diverse circumstances ; and 

 we perceive how valueless are the arbitrary characters of those 

 who try to frame artificial systems. Even the dentition of 

 the Mammalia, so paramount in the majority of cases, be- 

 comes quite a secondary means of distinction in the Marsu- 

 pialia ; and the structure of the bill in birds, so important 

 and corresponding a character in most instances, yet loses 

 almost all its value in the Certhiadae. Unquestionably, all the 

 yoke-footed tribes are very nearly related by affinity ; yet how 

 discordant are they in the details of their structure ! A single, 

 and comparatively trivial, resemblance in the organisation of 

 the foot becomes, in this instance, a character of the very first 

 importance. — Tooting, Surrey, August 13. 1836. 



