390 University of California Publications m Zoology [Vol. 13 



4. The Phylogenesis of Birds as Modified hy Morphology of Feathers 



As intimated above, distinct lines of evolution in the modification 

 of the structure of feathers are clearly shown by this study. After 

 making a careful analysis of these various lines of divergence, which 

 seem to be more or less orthogenetic in nature, a phylogenetic tree 

 representing the evolution of birds has been worked out, and is pre- 

 sented in fig. G (p. 391) . In so far as it is in accord with the facts of 

 morphology of the feathers, the classification presented by Knowlton 

 (1909) has been adhered to in the preparation of this evolutionary 

 tree, since it is believed that this classification is most nearly in 

 accord with the views of most of the leading ornithologists of the 

 present time, and most nearly embodies the evidence furnished by 

 recent work on comparative avian anatomy and morphology. In 

 all cases in which the evidence furnished by morphology of feathers 

 is distinctly not in accord with Knowlton 's interpretation of rela- 

 tionship, the classification has been altered so as to agree with the 

 facts of epiphyology presented in this paper. The phylogenesis 

 presented, therefore, is one which is based primarily on morphology 

 of feathers, but in which the system presented by Knowlton (1909) 

 has been adhered to in so far as there was no conflict. While it 

 is not supposed that such an interpretation of relationship is neces- 

 sarily the correct one, or that some other interpretation may not 

 be made which will better satisfy all the conditions of avian struc- 

 ture, it is hoped that the accompanying phylogenetic tree will be 

 of use to taxonomists in the embodiment of the facts presented in 

 this paper in the preparation of a system of classification which 

 will best satisfy the conditions of all branches of the comparative 

 morphology of birds. 



Transmitted April 11, 191Jt. 



