1907.] 



ORIGIN OF PLIGHT. 



235 



in time enable the yet caiiiivoi'ous and cursorial ancestoi- of 

 Birds to take long strides or leaps, much in the manner of a 

 domesticated Goose or of a Stork when starting, and ultimately 

 develop to actual feathers ; this epidermic cover would also raise 

 the temperatui'e of the body, and thus help to increase the 

 mental and bodily activity of these rapacious forms. The 

 possibility of such a development of flight is clearly shown b)'" 

 the somewhat analogous, but still more marvellous and nearly 

 paradoxical, yet not unfrequent, development of Flying-Fishes. 

 The marginal scales being originally the principal wing-element 

 in such a hypothetical foi'm, these parrs could attain quite a 

 considerable size without essentially altering the underlying bones 

 of the arm, a fusion of the carpal phalanges being only then 

 necessary, when in flight rigidity of this region became requisite. 

 Besides this, the continued use of the anterior flapping limbs as 



Text-fie'. 82. 



Hypotlietical reconstruction of a running " Pro- Avis." 



grasping-organs would also account for the feeble specialisation of 

 the digits in the Ornitholestes-like manus of Arclueopteryx, and 

 for the preservation of the claws in the Ostrich and Opisthocomus, 

 where, according to Pycraft, the temporary delay in the growth of 

 the distal pinions has been developed simply not to prevent the 

 claws from performing their still not unimportant function. An 

 eftbrt to condense these hypothetical changes into a drawing is 

 given in text-fig. 82, which might in consequent allusion to 

 Pycraft's analogous reconstruction be called a " Pro- Avis." 



The facts that even from the Eocene formation in most parts 

 of the world numerous big Ratites are known, which can only 

 have originated from badly-flying ground-birds, whereas in more 

 modern times the Ratites ai-e apparently vanishing from the 

 earth's surface, likewise find quite an easy explanation in the 

 hypothesis that in the Mesozoic times badly-flying ground-birds, 

 and Qiot tree-birds, were the prevailing forms. The individual 

 or ontogenetical development of every cursorial Carinate (for 

 example, every gallinaceous bird) would thus show us the exact 

 manner in which flight has been acquired. The true phylogenetic 

 value of the surviving " Palseognathse," with their body-temperature 



