HISTORY OF THE KIWI. 6? 



Nevertheless a true though small ploughshare-bone is formed by the 

 fusion of two or three vertebra;. As the only function of this bone is 

 to support the tail-quills its presence in Apteryx seems to indicate 

 that the ancestors of the bird had tail-quills to be supported. 



On the whole it will be seen that the study of the development 

 of the kiwi tends to lessen the gulf between it and ordinary birds, 

 and to show that its ancestors probably possessed many of the more 

 important and distinctive features which characterise the Carinatse of 

 to-day. The facts clearly indicate that the founder of the Apterygian 

 house had interrupted plumage, functional wings, an ordinary avian 

 tail, a keeled sternum, a double-headed quadrate, lateral optic lobes, 

 and a pecten in the eye, in other words that the ancestors of the 

 genus were typical flying birds and not bird-like reptiles. It would 

 seem, therefore, that the facts tell strongly against hypothesis (I) of 

 the origin of the Ratitse (diagram p. 5*). 



As to the relative probability of hypothesis (2) and (3) we have 

 unfortunately only detached observations on the development of the 

 other Ratitse, and have therefore to rely mainly upon comparative 

 anatomy. 



Of the eight characters enumerated above (p. 3), as separating 

 the Ratify from the Carinatse it will be noticed that the first five are 

 directly connected with the power of flight. We should expect to find 

 such adaptive characters in purely cursorial birds whether they arose 

 from a common stock or sprang 1 separately from early flying birds, 

 and as a matter of fact they occur to a greater or less extent in such 

 flightless birds as the Dodo, Weka, Notornis, etc., which we know 

 have no genetic connection with one another, but have independently 

 acquired the characteristics of Sightlessness. I think, therefore, that 

 the possession of the characters referred to, by the whole of the 

 Ratitae is no argument for the common origin. 



The peculiarity of the quadrate has been shown to be a secondary 

 matter, and we have left only the characters of the base of the skull. 

 These certainly form an excellent diagnostic character by which the 

 whole of the Ratitse are separated from the majority of the Carinatae, 

 but even here the distinction is not absolute for the Tinamous 

 approach in many respects more nearly to the Ratitse than to the rest 

 of the Carinatse. Still it seems probable that the various genera of 

 Ratitae must have diverged from the main line of descent at a 

 comparatively early period, though perhaps not earlier than some of 

 the existing orders of Carinatse. The Penguins, for instance, are far 

 more reptilian in their vertebral column and less typical in the 

 structure of their wings than the Ratitse. The Ostrich, however, 

 shows the unique and very reptilian character of two claws on the 

 wing, and the very general presence of wing-claws in the group is a 

 distinctly primitive character. 



Leaving the skull, in which the whole group shows primitive 

 characters, and the wing and related parts in which the resemblances 

 between the genera are largely adaptive, we find the range of 

 variation in the Ratitse to be very great indeed. Two genera (Apteryx 

 and Dinornis) have a normal 4-toed foot; in three others (Cassowary, 



* In this diagram (top of p. 5) the letter r should be placed above the origin of the line 



leading to Ratitce. 



