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, published 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 which 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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