448 ANNALS NEW YORK ACADEMY OF SCIENCES 



tive birds were arboreal reptiles with long scale-covered arms, and they 

 learned to fly after they had gone through a flying-squirrel-like stage, in 

 which the skin and scales acted as a passive patagimn and flight was 

 learned by skimming downward to the ground. The opposing view, ad- 

 vocated by Nopcsa and supported by Watson and Williston, was that 

 flight began from the ground upward, the primitive types being small 

 bipedal dinosaur-like reptiles which beat the air with their long scaly 

 forearms as they ran along the ground. Dr. Broom's view was that the 

 primitive birds were nearly related to the common ancestors of the dino- 

 saurs and pterosaurs and were related to the aetosaurs. That first they 

 hopped on the ground, and then hopped in the trees, after the fashion 

 of a tree kangaroo, before learning to skim down from the trees. 



The speaker had made comparisons of the skulls and skeletons of all 

 the principal types of reptiles and ancient types of birds and felt that 

 there was strong evidence for the view advocated by Abel, Broom and 

 others that the dinosaurs, pterosaurs, aetosaurs and birds were divergent 

 derivatives of small "diapsid"' reptiles most nearly allied to the aetosaurs 

 (Pseudosuchia). To him the evidence indicated that the pro-aves were 

 small arboreal quadrupedal reptiles, excellent climbers and of great ac- 

 tivity in the trees, leaping from branch to branch like lemurs and early 

 acquiring a grasping hallux and consolidated metatarsus. Hands much 

 elongate, as in such agile Primates as the gibbons, digits of the manus 

 (which in the terrestrial stage had already been reduced in number from 

 five to three, as in certain dinosaurs) elongate, provided with sharp claws 

 (used in climbing) and covered on the back with long scales. In short, 

 the speaker supported the conservative view that birds had arisen in some- 

 what the same way as had pterosaurs and bats, namely, from very active 

 arboreal animals, and he felicitated Mr. Beebe upon adding new and 

 'striking evidence for this view. He referred to the fact that birds and 

 mammals had originated at about the same period in the earth's history, 

 namely, during the arid Triassic period, and that the most distinctive 

 characteristics of both mammals and birds were associated with the 

 maintenance of a high and relatively stable body temperature. He 

 thought that the acquirement of feathers, and subsequently of the power 

 of flight, was at first a biproduct of the adaptations in the circulatory 

 system for raising the temperature of the body and in the integnment 

 for retaining the heat. 



Dr. Matthew outlined the arguments which had been directed by 

 Professor Thomas Barbour against certain features of his paper on Cli- 

 mate and Evolution, especially those relating to the former land connec- 



