Page:The Emu volume 3.djvu/13

(Official (Drgzm of the Jtustntlasian (Ornithologists' (Bnion. Birds of a feather.' Vol. III.] ist JULY, 1903. [Part i. The Cormorants of New Zealand : a Study in Variation. By Captain F. W. Hutton, F.R.S., Christchurch. ALTHOUGH everyone allows that the different kinds of animals have had common ancestors, it is acknowledged to be a very difficult task to draw up a genealogical tree with any approach to accuracy. No one, perhaps, can realize fully this difficulty unless he has himself tr ed to reconstruct some portion of it. Yet the temptation to try is very strong, because we see that if we could trace out the history of an order, or of a family, or even of a large genus, we should at once obtain most interesting information about the origin of variations. Indeed, it is only by comparing a large number of pedigrees that we can ever arrive at sound conclusions as to the cause of variations. When we feel this temptation very strongly upon us — when, indeed, it becomes irresistible — we should look out for a group of animals in which all the conditions of life are as simple as possible ; for this removes many difficulties and uncertainties out of our way. Among the sea-birds the conditions are simpler than among land-birds, and New Zealand is particularly well situated for their study. I have therefore chosen the New Zealand . Cormorants — generally known as Shags — as a test for current theories of variation ; not intending to make it a close and formal investigation of the species — for which our knowledge of the habits and changes of plumage of the birds is not yet sufficient — but merely a light sketch, showing the way to a more elaborate study at some future time. I must, however, say a preliminary word about pedigrees in general. When only two species are concerned, we have either A derived from B, or B derived from A, or both A and B derived from an extinct species, C. This last is probably often the case, but as we cannot reproduce the extinct species, and as probably one of the new species will bear a closer resemblance to the