BIRDS OF NEW ZEALAND. 25 



harshness in Apteryx owenii, and also different degrees of it — in A. haastii 

 certainly, caused by the prolongation of the rachis. There is a sexual 

 difference of colour in my specimens of A. haastii, the females being 

 lighter than the males. I have perhaps, therefore, though open to conviction, 

 yet to admit the specific difference of the two insular forms, northern and 

 southern (^A. mantelli and A. australis), the ups and downs of which 

 deserve a place in Burke's ' Vicissitudes of Families.' Mr. Bartlett 

 first made them two (Proc. Zool. Soc. 1850, p. 274j. Dr. Sclater next 

 restores unity (Proc. Zool. Soc. 1871, p. 496). Mr. Potts (' Transactions of 

 the New-Zealand Institute,' 1872, p. 194) now again splits them. Dr. Finsch, 

 as above, leans to Dr. Sclater's view ; while Dr. Buller, in his ' Birds of 

 New Zealand,' sides with Mr. Potts. On examination, for my own part, of 

 my series, I doubt this variation in plumage (if it constantly exists) to be 

 sufficient as a diagnostic distinction to ground a specific difference upon ; 

 and I found my opinion on facts bearing on climatal change observed on 

 the south coast of England. There is something peculiar (shall I say almost 

 mammalian) in the way in which the covering of the Apteryx is placed upon 

 its body. Let me here remind my readers that in most birds there is not an 

 uninterrupted covering of feathers, but they grow in tracts. It is not, 

 however, my purpose here to go into this subject in the way it deserves. 

 Those who wish to follow it out, replete with interest as it is, can consult 

 Nitzsch's ' Pterylography,' edited by Philip Lutley Sclater, M.A., Ph.D., 

 F.R.S., in English, pubHshed by the Ray Society. I may nevertheless 

 remark that the feathers grow all over the body of the Apteryx ; the skin 

 is like leather and does not much vary in thickness, it is very difficult to 

 relax, and water has little effect upon it. Christian Ludwig Nitzsch had not 

 an Apteryx to study ; but he says, " an uninterrupted covering of feathers 

 occurs in the genus Aptenodytes, Linn., in wdiich I have found it particularly 

 complete ; also in the Cassowaries, in which, besides the naked parts of the 

 head and neck, only the pectoral callosity has no feathers. Most birds have 

 an incomplete feather- covering Birds usually have spaces between the 



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