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Feb. 10, 1876] lines, and works preparatory to bringing the new lands under culture.

The interest on the above sum will raise it to 13,400,000l., but one-fourth of this will be granted as a subsidy by government, which will be amply compensated by the comparatively enormous addition to its small territory,

Of the 473,000 acres to be drained, four-fifths, as we have said, are of great value, composed as they are of a bed of more than a metre thick of the most fertile mud deposited for centuries by the Yssel and other rivers of which the Zuyder Zee is the receptacle. Onty one-fifth consists of land of less value and of sands which will be useful in constructing the base of the dike, or to establish large reservoirs, indispensable in all drainage work, for the reception of the waters until they can be conveyed to the sea. Deduction being made for the land absorbed by these works, by canals, dikes, roads, &c. &., there will remain upwards of 400,000 acres suitable for culture, and the selling value of which ought considerably to exceed the expenses of the enterprise. Every one must wish that this bold and really beneficent scheme may be carried out with complete success.

THE BIRDS OF NORTH-EASTERN AFRICA

ARON THEODOR VON HEUGLIN is well known as one of the most active and successful of the travellers and naturalists of Germany—one who may fairly rank with the Wallaces and Bates of our own country—as regards the extent of his researches. No man living has devoted more time and toil to the investigation of the Fauna of North-eastern Africa, and as regards the classes of birds and mammals, no man living has a better acquaintance with them. Twelve years passed on the coasts and islands of the Red Sea, in the marshes and jungles of the White Nile, and in the Highlands of Abyssinia, during which time constant attention was devoted to the observation and collection of animals have given Herr von Heuglin unrivalled opportunities for amassing this knowledge, to which his skill as an artist has contributed additional facilities, Soon after returning from his last journey in 1865, Herr von Heuglin planned a general work on the Omithology of North-eastern Africa to embrace all the notes and observations collected during his different excursions, together with the information acquired by the study of specimens from these countries already existing in the continental museums. In 1869, the first part of the present work was issued, but its large extent hindered its progress, and the author was called away to join the German Expeditions to Nova Zembla and the extreme north, to which he was attached as naturalist. It was not, therefore, until the close of last year, or, we believe we may say until the beginning of the present year, that the concluding part of the Ornithology of North-eastern Africa was issued from the press. Completed, it now forms four volumes, illustrated by fifty-one coloured plates and a map of the region of which it treats, and is by far the most perfect work on the subject hitherto published. Prior to the completion of the present work Rüppell’s Atlas, and other publications were, so far as regards Nubia and Abyssinia, the only works of reference, whilst of the district of the White Nile so fully explored by Von Heuglin, very little was known except from fragmentary notices. In the present extended work the ornithology of the whole of these countries, together with that of Egypt, the Red Sea, and Northern Somali-land, are treated of together. The sum of species of birds is thus raised to a high figure, no less than 948, of which upwards of 200 are entirely confined to North-eastern Africa, European species are likewise numerous in these countries. Northern Africa being, as is well known, the favoured haunt of our summer migrants during the winter season. Upwards of 300 European birds thus come to be included in Herr von Heuglin’s list. The plan of our author's work is good, though it seems to be rather adapted for the home student than for the field-naturalist, neither family nor generic characters being included. But we observe with pleasure that specific diagnoses are given in Latin to all except the best known species, which, after the contumely that certain imperfectly educated naturalists have recently thought fit to bestow upon that classical tongue, is worthy of all praise. The references to former authors are also numerous, and, so far as we have been able to test them, more accurate than is too often, unfortunately, the case in works of this kind. But the great feature of the book are the observations on the habits and localities extracted from the note-books of the unwearied author. These are much more numerous, and better put together than in almost any other work on foreign ornithology with which we are acquainted. Errors and omissions there are no doubt, and must be, in a work of this magnitude, as indeed is sufficiently evident by the many pages of additions and corrections annexed to the fourth volume, but Herr von Heuglin has spared no trouble to bring his Ornithology of North-eastern Africa up to date, and his volumes will long remain a standard work of reference upon the birds of these districts, which are now attracting so much attention in civilised Europe.

FERTILISATION OF FLOWERS BY INSECTS XIII. Additional Alpine Flowers adapted to Cross-fertilisation by Lepidoptera.

HE same relation which I have shown to exist between Daphne Mezereum and striata, Primula officinalis and villosa, Rhinanthus crista-galli and alpinus (NATURE, vol. xi. p. 110), exists also between Viola tricolor and calcarata, the former inhabiting the plain and the lower mountainous localities, and being adapted to cross-fertilisation by bees; the latter, on the contrary, inhabiting the higher Alpine regions, and being adapted to fertilisation by butterflies.

Viola calcarata is found in the Strela pass towards Davos (2,300 metres above the sea-level), and in the rocky slopes of Piz Umbrail towards Quarta Cantoniera (2,600-2,700 m.) in such plenty as to appear from some distance like a blue carpet of flowers. In the latter locality, July 15, 1875, I saw these flowers assiduously visited by different butterflies, of which I caught two specimens of Colias phicomone, and three Erebia laprona E. (manto, W.V.). The modifications of structure by which the flowers of V. calcarata (Fig. 82-85) differ from those of V. tricolor (Fig. 15-22, NATURE, vol. ix. p. 46), besides their eminent conspicuousness, so frequently found in Alpine flowers, are such as prevent Diptera and probably also Apidæ from sucking the honey, whereas butterflies, for which alone the honey is reserved, cannot suck it without effecting cross-fertilisation. For the spur, which generally is only 3-4 mm. long in V. tricolor, exceeds in this species 10 mm. in length, its width being only 1 mm, in the vertical, and scarcely half a millimetre in the horizontal direction; and the stigmatic knob, provided with a labiated appendage, as in the large-flowered form of V. tricolor, lies so closely pressed against the under lip, that no proboscis of any butterfly can enter the spur without grazing the stigmatic lip. The pollen-grains, when they fall out of the anthers, collect in the hairs which clothe the furrow of the under lip (po Fig. 85), and no proboscis of a butterfly can be inserted into the spur without being smeared with pollen-grains, which, in the flower next