452 



ISLAND LIFE. 



[part II. 



the Cretaceous period, the two great forms of birds — those with 

 a keeled sternum and fairly-developed wings, and those with a 

 convex keel-less sternum and rudimentary wdngs — already 

 existed side by side ; while in the still earlier Archseopteryx of 

 the Jurassic period we have a bird with well-developed wings, 

 and therefore probably with a keeled sternum. We are evidently, 

 therefore, very far from a knowledge of the earlier stages of 

 bird life, and our acquaintance with the various forms that have 

 existed is scanty in the extreme ; but we may be sure that birds 

 acquired wings, and feathers, and some power of flight, before 

 they developed a keeled sternum, since we see that bats with no 

 such keel fly very well. Since, therefore, the struthious birds 

 all have perfect feathers, and all have rudimentary wings, which 

 are anatomically those of true birds, not the rudimentary fore- 

 legs of reptiles, and since we know that in many higher groups 

 of birds — as the pigeons and the rails — the wings have become 

 more or less aborted, and the keel of the sternum greatly 

 reduced in size by disuse, it seems probable that the very 

 remote ancestors of the rhea, the cassowary, and the apteryx, 

 were true flying birds, although not perhaps provided with a 

 keeled sternum, or possessing very great powers of flight. But 

 in addition to the possible ancestral power of flight, we have 

 the undoubted fact that the rhea and the emu both swim 

 freely, the former having been seen swimming from island to 

 island off the coast of Patagonia. This, taken in connection 

 with the wonderful aquatic ostrich of the Cretaceous period 

 discovered by Professor Marsh, opens up fresh possibilities of 

 migration; while the immense antiquity thus given to the 

 group and their universal distribution in past time, renders 

 all suggestions of special modes of communication between the 

 parts of the globe in which their scattered remnants now 

 happen to exist, altogether superfluous and misleading. 



The bearing of this argument on our present subject is, that 

 so far as accounting for the presence of wingless birds in New 

 Zealand is concerned, we have nothing w^hatever to do with 

 any possible connection, by way of a southern continent or 

 antarctic islands, with South America and South Africa, 

 because the nearest allies of its moas and kiwis are the 



