234 BARON NOPCSA ON THE [Feb. 19, 



Tinamous, possessed nob only free vertebrae, but even elongate, 

 Dinosaurian-like neural spines in the dorsal region, and this 

 because also in this case, for running, strength ha,d to be united 

 with mobility in the dorsal region, whereas for flight, as already 

 mentioned, strength and rigidity seem to be the qualities required, 

 so that the neural spines become to a certain extent useless. It 

 is especially to the cuiious dorsal and caudal vertebi'fe of ^^pyornis 

 that I should like to draw attention. Probably mobility is one 

 ■of the reasons why in the flightless Hesperornis saddle-shaped 

 vertebrte were developed at a period when Ichthyornis still showed 

 biconcave articulation, although I am quite aware that perhaps 

 other explanations will have to be sought for, since also in other 

 ways Hesperornis indicates a more specialised form, and this not 

 only by its wing-bones being already reduced, but by exhibiting a 

 certain tendency to lose its teeth, since these are no longer placed 

 in distinct sockets as in Archmopteryx and Ichthyornis, but in a 

 furrow. 



If we, after these preliminaries, now suppose that Birds, before 

 attaining the Archceopteryx-stiite, originated from quadrupedal 

 arboreal animals and only after having learnt to fly became bi- 

 pedal, it is difiicult to understand why they in general show Dino- 

 saurian affinities, why they did not use both hind and fore limbs 

 to the same extent for flight as they would have done for arboreal 

 locomotion, why the bones of the pectoral region and of the wings 

 show more primitive traces than the hind pai'ts of the body, and 

 why they did not, like all other quadrupedal flying animals, 

 develop a patagium ; whereas, if we consider that in Archmopteryx 

 the anterior extremities, though bearing the most important 

 ■ectodermal pinions, are less modified than the posterior extremities, 

 which are already perfectly bird-like, and if we then suppose that 

 Birds originated from bipedal Dinosaur-like Reptiles, it is easy to 

 understand what induced the Birds to attain an Ai-chceojiteryx- 

 like stage of evolution, for at first a certain amount of bipedal, 

 and only afterwards a volant, modification would be required. 



While we can safely state that a bipedal animal never could or 

 did develop a patagium without giving vip bipedalism, this cannot 

 be said of feather-bearing forms, for we may quite well suppose 

 that hirds originated from hipedcd long-tailed cursorial reptiles 

 tvhich during rimning oared along in the air hy flapping their 

 free anterior extremities. If Dinosaurs had bird-like pulmonary 

 appendages, as indicated by the pneumaticity of the skeletoia, such 

 movement would only have been of advantage for the respiratory 

 organs (the pneumatic foramen occurring sometimes in Moa -bones 

 would therefore be an atavistic feature, and the loss of pneumaticity 

 would be a parallel to the same change in the Dinosam^ian sub- 

 class). At this point the pulmonary appendages of Chameleons 

 have also to be taken into consideration. A double running and 

 flapping action would — somewhat in accordance with Pyci-aft's 

 views on this subject — subsequently easily lead to an enlargement 

 of the posterior marginal scales of the antibrachium, and at the 

 same time produce a certain amount of bipedal specialisation. 



By gradually increasing in size, the enlarged but perhaps still 

 horny hypothetical scales of the antibrachial margin would 



