390 C. J. Sundcvall on the Wings of Birds. 



greater value merely because it is derived from tlie relations 

 of internal parts, of whicli the many exceedingly unnatural 

 systematic classifications, founded upon so-called anatomical 

 characters^ are a clear proof "^. 



Thus what is characteristic may just as easily be over- 

 looked in the internal as in the external parts ; but, should 

 it be correctly grasped, every part of an animal's surface or 

 covering ought to furnish characters just as reliable for the 

 animal's affinities as the inner or so-called nobler parts ; for 

 the cause, predetermined in the egg, Avliich makes an animal 

 belong to one or the other class, order, family, species, &c., 

 has continued to act uninterruptedly throughout the whole 

 development upon every part of the animal's body, both exter- 

 nal and internal, and has necessarily left behind some impress 

 which may be distinguished from all others. But as different 

 causes must produce different effects, it becomes impossible 

 that any particular part in an animal can be exactly similar 

 to a part in another animal of a different order, genus, &c. 

 From a physiological point of view, indeed, the internal parts 

 may be regarded as more important than the external ; but 

 zoographically we must regard the external parts as possess- 

 ing an equal if not greater value, because the characters 

 derived from them can be easily recognized and examined in 

 the specimens of natural products which usually occur, 

 which is not the case with those founded upon the internal 

 parts ; and I venture to maintain that only external form- 

 characters ought to be employed in zoographical diagnoses, 

 and also that the external parts always present such charac- 

 ters as express quite clearly the affinities of the species, 

 although these characters may not always lie open to super- 

 ficial observation. The wing-feathers may therefore furnish 

 just as important characters as any other part of a bird's 

 body, and an accurate knowledge of them may be of the 

 greatest value in ornithology. 



* E. g. the classifications of tlie Arachnida from tlie organs of respira- 

 tion, the divisions in the class Vermes in accordance with differences in 

 the nervous system, the arrangement of the Gasteropoda according to 

 the branchiae, &:c. 



