1868.] PROF. HUXLKY ON THK ALECTOROMORPH.E. 313 



course, no more obliges us to believe that the original Gallo-colunibiile 

 bird was just like Pterocles, than the fact that a given nobleman is 

 directly descended from a Norman baron compels us to think that a 

 photograph of the one would serve for a portrait of the other. 



I cannot understaud the general resemblances combined with the 

 particular differences of Opisthocomus, without the supposition that 

 it is a highly modified form derived from the primitive Gallo- 

 columbiue stock. 



But the resemblances between the Gallo-columbines and the 

 Ohara(lriomorph(E. (or rather the Aleo-pluviaUne series) are such 

 that, if the theory of evolution be correct, they also must have had a 

 common stock ; and I presume that the Turnicimorphce may be the 

 nearest representatives of that stock. 



All these, again, are modifications of that primary form of the 

 Carina/cB of which I am disposed to think Tinamus the only living 

 representative ; while the Ratiiee are the scanty modern heirs of the 

 great multitude of ornithoid creatures which once connected Birds 

 with Reptiles. 



V. The geographical distribution o/ Alectoromorphee. 



The geographical distribution of the Alectoromorpha is related in 

 a highly interesting manner to that classification of its members 

 which has been shown above to flow from the comparison of their 

 most important anatomical characters. 



Thus, the Peristeropodes occupy a vast area which lies largely, 

 though by no means whoUj^ upon the southern side of the equator. 

 All distributional boundary lines can be but roughly and broadly 

 drawn ; but such a line, limiting the northern extension of the Periste- 

 ropodes, would cross the American continent on the northern frontier 

 of Mexico, and then, sweeping so\ithvvard and eastward across the 

 Atlantic round the Cape of Good Hope, would leave Africa alto- 

 gether to the north *. Passing south of India and Indo-Malaisia, 

 but north of the Nicobar islands, tlie boundary in question would 

 coincide with what may be called " Wallace's line," between the 

 Indian and the Papuan divisions of the Malay archipelago. But it 

 would run northward as far as the Phihppines, and, passing between 

 them and Formosa, would trend southward and eastward to the 

 Samoan archipelago. (See Map, p. 294.) 



The Peristeropodes are not found on the north side of the irre- 

 gularly waved line which has been thus defined. The Alectoropodes, 

 on the other hand, occupy the great northern region thus excluded, 

 only a few Quails, Odontophorines, and Meleagris extending to the 

 south of the frontier line. 



Thus, if we consider the distribution of the AlectoromorphxB alone, 

 the whole surface of the globe must be primarily subdivided into 

 two principal areae — a northern and a southern. And I think it is 



* I havd not seen the skeleton of tlie genus Mcsitcs ; but Dr. Sclater, who has 

 exauiined tlie only .specimen ol' thi.s Madekass bird which has been brought to 

 Europe, tells inc that lie does not believe it to be Gallinaceous. 



