Page:Auk Volume 13-1896.djvu/147

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VO !'s0 ln ] LUCAS on the Tongues of Birds. T(X) THE TAXONOMIC VALUE OF THE TONGUE IN BIRDS. BY FREDERIC A. LUCAS. A recent paper of mine on the tongues of Woodpeckers con- cluded with the statement that " altogether the evidence favors the view that (external) modifications of the tongue are directly related to the character of the food, and are not of value for classification."' Dr. Allen, in noticing this paper in ' The Auk ' for October, 1895, says: " Granting that the facts are as stated, we are reluctant to agree with Mr. Lucas's conclusions, for on the same grounds we should have to rule out of the list of taxonomic characters any structural feature adaptively modified to special modes of life, and these involve, in a more or less marked degree, every part of the organism." In writing thus, Dr. Allen has drawn attention to what is per- haps the greatest of the many difficulties which beset the ambitious taxonomist who would venture upon the classification of birds, since, as Dr. Allen says, every part of a bird's organism, whether external or internal, bears marks of modification for some purpose. Consequently it is practically impossible to use in classification those characters alone which are due to morphological variations, but it is a truism that those characters which rest on a good mor- phologic basis should have precedence over those which are solely due to adaptation to some particular purpose. Now it is by no means easy to certainly discriminate between these two things for a physiological adaptation may be of such long standing as to have taken on the guise of structural modification. Thus the absence of a keel to the sternum, the openness of the angle formed by the scapula and coracoid, and the fusion of these last two bones are all secondary characters, and yet they have been accorded a high, if not the highest, rank in classification. To illustrate the extent to which adaptive features may obscure the relationships of a bird, it may be worth while, for the benefit of the younger readers of ' The Auk,' to recall that on the evidence of the tibia Owen put Cnemiomis with the Moas, while Parker, guided by the sternum, assigned it a place near the Rails. Each of these eminent anatomists was led astray by purely adaptive