36o THE BIOLOGY OF BIRDS 



Two other points may be noted. It must not be sup- 

 posed that the important difference between the struthious 

 " Palaeognathine " palate and the carinate " Neognathine " 

 palate necessarily indicates a dual origin of Ratitae and 

 Carinatae. Mr. Pycraft's studies of the development of the 

 palate show that the Neognathine palate is derivable from the 

 other. But there is another consideration, which shows how 

 difficult and uncertain all these discussions are, namely the 

 question whether the Running-Birds form a coherent 

 *' order," or whether they may not represent an assemblage 

 of forms of diverse origin which " went back " at an early 

 stage in the evolution of birds when the palate was still at 

 the palaeognathine grade. 



§ 8. Flying Birds 



According to Mr. Pycraft, the birds with a neognathine 

 palate split up early into two branches, each of which divided 

 again, so that four legions may be recognised : — 



A. Colymbomorphs : Penguins, Grebes, Divers, Petrels. 



B. Pelargomorphs : Storks, Herons, Anserine birds. 

 Falcons, etc. ; Pelicans, Gannets, Cormorants, etc. 

 (Steganopods). 



C. Alectomorphs : Gallinaceous birds — the Fowl tribe, — 

 Rails, Cranes, Plovers, Gulls, Auks, Pigeons, Sand-Grouse. 



D. Coraciomorphs : Cuckoos, Parrots, Hoopoes, Horn- 

 bills, Woodpeckers, Barbets ; Rollers, Bee-Eaters, King- 

 fishers ; Owls, Swifts, Humming-birds, Mouse-birds ; and 

 the great host of perching birds or Passeres. 



§ 9. The Process of Evolution 



It is useful to ask at this point whether any general idea 

 can be formed as to what has taken place in the establishment 

 of 10,000 or more different species of Flying Birds ? 



We must think of each type as having an equipment of 

 hereditary items or factors, corresponding to characters in 

 the full-grown birds. These hereditary factors are like 



