Black-back are darker than those of the Herring, but the difference if anything is very slight; but the head and neck and the centres of the feathers of the back of the Lesser Black-back are darker,--more of a dark smoky brown than those of the Herring Gull: this difference of colour is even more apparent on the under surface, including the breast, belly, and flanks. The shoulder of the wing and the under wing-coverts of the Lesser Black-back are much darker, nearly dull sooty black, and much less margined and marked with pale whitey brown than those of the Herring Gull. The dark bands on the end of the tail-feathers of the Lesser Black-back are broader and darker than in the Herring Gull: this seems especially apparent on the two outer tail-feathers on each side; besides this, there is a slight difference in the colour of the legs, those of the Lesser Black-back showing a slight indication of the yellow of maturity. I have noted these distinctions both from living specimens of both species which I have kept, and noted their various changes from time to time, and from skins of both: unfortunately the two skins of the youngest birds I have are not quite of the same age, one being that of a young Herring Gull, killed at the Needles in August,--the other a young Lesser Black-back, killed in Guernsey in December; but I do not think that this difference of time from August to December, the birds being of the same year, makes much difference in the colour of the feathers; at least this is my experience of live birds: it is not till the next moult that more material distinctions begin to appear; after that there can be no doubt as to the species. Two young Herring Gulls which I have, and which I saw in the flesh at Couch's shop just after they had been shot, seem to me worthy of some notice as showing the gradual change of plumage in the Herring Gull; they were shot on the same day, and appear to me to be one exactly a year older than the other; they were killed in November, when both had clean moulted, and show examples of the second and third moult. No. 1, the oldest, has the back nearly uniform grey, and the rump and upper tail-coverts white, as in the adult. In No. 2, the younger one, the grey feathers on the back were much mixed with the brownish feathers of the young bird, and there are no absolutely white feathers on the rump and tail-coverts, all of them being more or less marked with brown. The tail in No. 2 has the brown on it collected in large and nearly confluent blotches, whilst that of No. 1 is merely freckled with brown. But perhaps the greatest difference is in the primary quills; the first four primaries, however, are much alike, those of No. 1, being a little darker and more distinctly coloured; in both they are nearly of a uniform colour, only being slightly mottled on the inner web towards the base; there is no white tip to either. In No. 1 the fifth primary has a distinct white tip; the sixth also has a decided