324 ME. J. L. BONITOTE ON THE [June 18, 



longitudinal stripe down the centre of each vane. This type is 

 found in the young of Nycticorax and also of Ardea cinerea and 

 A. purpurea ; this marking was presumably assumed long ago, as 

 even in young birds we get no trace of the earlier stages. In the 

 Bittern, however, similar markings exist and we also find connecting 

 bars, these features being especially well marked on the scapulars; 

 and so we may be entitled to assume that in Ardea the former 

 pattern was derived along the same line. 



Among the Anatidae we may notice that the barred form is 

 the commonest and most usual type. Taking Anas boschas as our 

 example, and the feathers on the breast in particular, we may 

 notice that in the immature bird the feather is brownish with a 

 longitudinal stripe ; this pattern also persists in the adult female. 

 In the male the feathers are self-coloured on the breast, but with 

 minutely vermiculated bars on the chest ; in his summer dress, 

 however, the pattern of the feathers is barred and not longi- 

 tudinally striped, but otherwise similar in colour to the female. 

 The bars vary greatly in their development, but for the most part 

 they are not strikingly defined. 



Over the Common Partridge (Perdix cinerea) — which we may 

 take as practically typical of the group to which it belongs — it may 

 be worth while to spend a few minutes. The most conspicuous 

 parts of the Partridge's feather are the longitudinal white stripes . 

 along the rhachis. These stripes occur in the very young bird on 

 almost all the feathers both of the back and front; but in the adult, 

 although far more conspicuous, they are restricted to the flanks and 

 scapulars. Starting with a very young bird which has just got its 

 first feathers, we may notice that the feather has a narrow light 

 centre boimded on either side by a longitudinal dark stripe, which is 

 again succeeded by a lighter area. In most of the feathers this 

 stripe appears uniform and unbroken, but generally a few isolated 

 feathers may be found in which either the stripe on one side or 

 the other is abruptly broken by a light bar, or the stripe shows 

 signs of being darker and thicker in certain places. It is therefore 

 obvious that this stage is not developed along the line in which 

 the proximal pattern has disappeared and the terminal bar has 

 grown out with elongated arms until the centre becomes obliterated, 

 leaving the arms, but that each of these longitudinal dark stripes 

 is made up of portions of successive bars. The key to this 

 system is that in the youngest bird the light centre widens out to 

 form a white tip similar in shape to that of the Nutcracker, and 

 noticed previously in this paper when dealing with the "Wren. 

 The method of evolution will be most clearly understood by a 

 study of the figures (see Plate XX. figs. 2, 3 & 4). 



The next order which we will notice is that of the Limicolae ; 

 they show comparatively few feathers of interest from the point 

 of view of pattern, and may be discussed in a few words. 

 They are all rather primitive, and except in a few cases hardly 

 reach the complete barred stage. The Norfolk Plover shows a 

 very primitive form, the pattern being chiefly mere longitudinal 



