The statistics furnished by Herr Gätke under these several headings are some of them very curious, and to those who are not professed ornithologists will probably be new.

"A large portion of the migrants," says Herr Gätke, "travel within an east to west, another within a north to south, line of flight. Species which fail to find satisfactory winter quarters in the western countries of Europe, on arriving in these districts deviate from their westerly course, and pursue their journey in a southward direction.

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Those, on the other hand, whose autumn migration takes place in a southerly direction, persevere in their course from their breeding-station to the end of their journey, though some may make a more or less considerable deviation to the east.

"The predominant mode in which the migratory movement is performed is in a broad front or migration column, which in the case of species migrating to the west corresponds to the latitudinal range of their breeding area, and in those migrating southwards to the longitudinal extent of their nesting stations."

The view much discussed in recent years, that migratory birds follow the coast lines, the drainage area of rivers, or depressions of valleys as fixed routes of migration, can, in the opinion of Herr Gätke, hardly be maintained. Too many facts, to some of which he refers, are at variance, he says, with this assumption. Direct observations in Heligoland have established the fact that in autumn the migration proceeds from east to west, and in spring in the opposite direction. Not all birds, however, reach their winter quarters by proceeding in a westward direction, some being sooner or later obliged to turn southwards in order to reach their destination.

The following curious observation shows the close attention which Herr Gätke has paid to the subject on which he writes:

"During the autumn migration it frequently happens that when out at sea birds are carried into air currents stronger than is suitable to their line of flight, a violent S.E. wind being especially unfavourable. To escape this wind blowing obliquely through their plumage from behind, they turn their body southwards and appear to be flying in that direction. This, however, is not the case. They do not make the least forward progress to the south, but their flight is continued in as exact a westerly course, and with the same speed, as though the birds were moving

under favourable conditions in the direction of the long axis of their bodies. This is shown in the most convincing manner by such flocks as happen to pass immediately over the head of the observer."

The altitude at which birds fly, and the velocity they attain during migration, are subjects to which Herr Gätke has paid special attention, and on which he discourses at considerable length. From experiments which have been made by other writers to test the average speed of birds in flight,-swallows, game-birds, falcons, and homing pigeons,*-we are inclined to think that Herr Gätke has overrated the speed at which migratory birds usually travel, except when moving before the wind; but, as he gives reasons for his conclusions, it would not be possible to refute his statements without a more complete examination of the details than could be here attempted.

Herr Gätke's work is an extremely valuable one to naturalists, not only because it embodies the results of fifty years' observations made at one particular station, and on that account most reliable, but also because it contains so many suggestive remarks which deserve the consideration of other observers, who, though less favourably situated than himself, may be able one day, with the aid thus afforded them, to deal effectively with some of the problems of migration as yet unsolved.

ON THE RACES AND VARIETIES OF THE POLECAT. BY ADOLPHE DRION, JUN.

IN the Bulletin de l'Académie Royale des Sciences, des Lettres et des Beaux-Arts de Belgique' (ser. 3, t. xiv. pp. 365-68), a Belgian naturalist, M. Drion, Jun., has published an article with this title, which has probably escaped the notice of the majority of our readers. Whether his views on this subject are to be accepted seems to us questionable, considering the extreme variation in colour to which the Polecat is liable. This animal has now become so rare in most parts of England, in consequence of being trapped by gamekeepers on every possible oppor

*See Zoologist,' 1886, p. 299; 1888, p. 308; 1892, p. 362; 'Nature,' 1887, pp. 335, 480, 552, 599; 1888, pp. 369, 474; Field,' 1887, pp. 114, 242 and 1891, Dec. 5th.

tunity, that it would probably be difficult to carry out such a series of observations as those made by M. Drion, for want of a sufficiently large number of specimens for examination.

It may be of interest, however, to know what M. Drion's views are on this subject, and we accordingly append a translation of his article. He says:

"In Belgium there are two races of Polecat, the yellow and the black race. The yellow race has a rather short body; it is high on its legs; the claws are lengthy and straight; the under parts of the body, the thighs, and the feet, are of a very dark colour, but the flanks are golden yellow; the contour of the eyes and muzzle is of a yellowish tinge, approaching to grey; the tail brown and bushy, especially in the old ones. The Yellow Polecat generally haunts marshy places and the banks of streams, but occasionally dry places and the neighbourhood of dwellings. Averse to all training, it becomes shy and timid in captivity.

"The Black Polecat is of a more elongated form. It is not so high on its legs as its congener; its claws are shorter and more curved. The ears, the contour of the eyes, and muzzle, are of a pure white, which contrasts strangely with the dark fur; the coat is black, although the sides show a washed-out yellowish tinge. It usually affects dry places in the neighbourhood of dwellings, but is occasionally found in river-banks and marshes. In captivity it is untamable. Not only is it, like the Yellow Polecat, rebellious to any kind of training, but it is fierce and bloodthirsty, even furiously attacking the hand that feeds it. Besides these two races, characterized by an appreciable difference in the structure of the body, the peculiar shape of the claws, the colour of the coat, and by their habits, there are intermediate shades which result from crossing. These are (1) the brownish yellow Polecat a cross between the pure yellow and the pure blacksubelongated and of medium shape. (2) The bronze goldenyellow. (3) The citron-yellow. The citron-yellow. (4) The grey, mixed with tarnished-yellow. (5) The Patois à plastron, an accidental variety. "The Polecats shaded with bronzed golden-yellow, citron. yellow, and à plastron, are the progeny of the brownish-yellow Polecat crossed with the pure yellow or the black.

"The grey mixed with tarnished-yellow differs completely from the others by its coat, which is of a much more uniform tint over the whole body.

"I have not been able to decide upon this point, namely, whether it constitutes a distinct race from the two preceding; whether it results from a cross; or whether, in fact, it is not an escaped Ferret. The last-named seems more likely, for the Polecat-ferret is less sensitive to cold than the albino Ferret; and consequently much less liable to die of cold in a state of liberty. In the Natural History Museum at Brussels there is a young black Polecat and a young grey one, labelled 'young,' without comment. The difference in colour between these two mounted specimens is striking. The grey Polecat closely resembles the half-bred Ferret. It would seem that this was the result of a cross between a dusky Polecat and an albino. The Polecat à plastron is remarkable for a white or yellow spot on the throat.

"I have a grey specimen with a white throat, and a black specimen with a throat equally white; and I have seen black ones which have a yellow throat. The brownish-yellow Polecats are the commonest. The yellow ones and the black ones are somewhat rare. The two last-named are examples of the pure breed. The grey Polecat and those with the light throat are rarely met with. My observations are founded upon two hundred specimens of all shades, of which one hundred and eight were caught by myself, and ninety-two were brought to me by keepers.

"It was long supposed that the difference in colour between the yellow and the black Polecats was merely the result of local influences-accidental or climatic-or of age or sex. I can testify to the contrary, because I have caught yellow Polecats, male and female, young and old, showing the distinctive characteristics of their respective races. At all seasons I have caught black ones, young and old, male and female, from one end of the year to the other. My experience, moreover, confirms these views. In the month of September I secured two young male Polecats, yellow and black. I kept them in separate cages for three years, during which time there was, positively, neither change of colour nor change of shape. The yellow one remained yellow in summer, at the period of moulting, and in winter. The black one always retained the same dark coat. I noticed that the black one was much fiercer and bolder. He was also more active, and generally climbed to the top of his cage when disturbed. The yellow one was timid and less active in his

movements. He was always scratching at the floor of his cage, trying, as it were, to dig a burrow. In those of intermediate colour, the claws of those whose pelage are yellowish are more slender and less curved than the claws of the dusky Polecats. To appreciate the difference in the claws, one must secure examples of pure breed. The very young Polecats, of both varieties, scarcely a few months old, are dark. It is difficult, therefore, to decide at an early age whether they belong to the yellow or to the black race. The best furs are those of the pure yellow Polecat, the bronze-yellow, and the citron-yellow. The skins of the black Polecats are not much esteemed, and rarely come into the market. Finally, in every case, the adult male is always about one-third larger and stouter than the female."

THE LONG-TAILED FIELD MOUSE OF THE OUTER HEBRIDES: A PROPOSED NEW SPECIES.

BY W. E. DE WINTON.

In the summer of 1894 I had the good fortune to visit the island of Lewis in the Outer Hebrides, and there found the Longtailed Field Mouse very common, as recorded in the 'Annals of Scottish Natural History' for January, 1895, p. 53.

This mouse is very distinct from Mus sylvaticus of the mainland, and I have only delayed in describing it as I was in hopes of again visiting the island this year. But though I have been unable to carry out my wish, the next best thing has happened; for my friend R. W. Pinney, a keen naturalist, has been shooting in the island of Barra, and has kindly sent me specimens, bringing up the number of my collection to over twenty, and confirming my opinion that this peculiar form would be found on all the islands of the group on which Mus sylvaticus occurs. This will show that I am not in a hurry to add to the British list before having fair material to work upon.

I propose for this mouse the name of

MUS HEBRIDENSIS, sp. n.

Resembling Mus sylvaticus in general form and colour, but having far smaller ears in proportion to its size; longer hind feet, which are also much stouter in the males; the form generally of