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it presents no trace of structure. It follows the contour of the facets on the surface of the deeper layer. The deeper layer consists of numerous thin laminæ, each being composed of a vast number of parallel fibres. It further appears to consist of hexagonal prisms, vertical to the surfaces of the cornea, and to the laminæ of which it is composed. These prisms are not, however, separable, although the lamina and the fibres of which they are composed are easily separated by treating the section for a short time with a solution of caustic potash. The surfaces of this deeper layer of the cornea may be seen to be covered with convex facets, a facet corresponding to either extremity of each vertical prism, the external facets being, however, best marked. In section this layer is seen to be marked by several hundred crenated lines, caused by the laminæ of which it is composed ; the crenations follow the contour of the facets, the middle layers being almost or entirely without crenations. These lines, as well as the indications of the division of the cornea into hexagonal prisms, are best marked in the external portion of the layer. Numerous minute nuclei appear between the laminæ. When viewed by the aid of polarised light and a selenite, these modifications of structure all become beautifully apparent. Both layers of the cornea polarise, and the colour of the transmitted beam varies from red to green, according to the thickness of the section simultaneously in both."

How to Mount Spiders for Cabinets.—In M. Thorell's fine 4to on European Spiders, which singularly enough is published in Upsala, and yet printed in the English language, the following instructions are given :-" The spider is first killed, either by the vapour of ether or by heat, and is impaled by an insect-pin, which is passed through the right side of the cephalo-thorax; the abdomen is then cut off close to the cephalo-thorax, and the cut surface dried with blotting-paper. The head of another insect-pin is cut off, and the blunt extremity introduced through the incision into the abdomen, up to the spinners. The abdomen thus spitted is inserted into a large test-tube held over the flame of a candle, the preparation being constantly rotated till dry, avoiding the extremes of too much or too little heat-the firmness of the abdomen being tested every now and then with a fine needle, till it is so firm as not to yield to pressure; the front extremity of the pin is now cut off obliquely, and the point thus made inserted into the cephalo-thorax, the two halves of the body being thus again brought into apposition. The animal may then be mounted as usual.”

New Tailless Batrachians.--At the meeting of the Zoological Society on June 9 Dr. A. Günther communicated an account of the species of tailless batrachians recently added to the collection of the British Museum, amongst which was a new diminutive frog, recently discovered by Dr. Cunningham in Fuegia, and proposed to be called Nannophryne variegata.

African Swallows.--At a meeting of the above-mentioned society on May 12 Mr. R. B. Sharpe read a paper containing a full account of the swallows (Hirundinidee) of Africa, and pointed out their characters and geographical distribution. Particular attention was drawn to the affinities of the African Hirundinide with those of the New World, and also to the representation of various species by smaller races or sub-species throughout the Æthiopian region. Thirty-eight species of swallows were enumerated,

of which number thirty were stated to be peculiar to the continent of Africa, and two to Madagascar and the adjacent islands. Two species only were common to India and Africa, and the remaining four were migratory throughout the Palæarctic and Æthiopian regions.

The Prosectorship in the Zoological Society. It is rumoured, and we believe with some foundation, that this post, vacant by the retirement of Dr. James Murie, is not likely to be filled up for some considerable time.

Dimorphism in the Higher Worms.—The American Naturalist for March gives an abstract of M. Claparède's observations on the Annelids, published in the Bibliothèque universelle. It states that in his account of the Annelids of the Gulf of Naples he confirms the discovery of Malmgren, that Heteronereis is a form of the old genus Nereis. He states that Ehlers, in 1867, in his Die Borstenwürmer, a work on the higher Annelids, has shown the undoubted specific unity of Nereis cultrifera and Heteronereis lobulata ; of Nereis pelagica, and Heteronereis grandifolia ; of Nereis Dumeriliï and Heteronereis fucicola ; of Nereis vexillosa, and Heteronereis Middendorfii ; of Nereis fucata and Heteronereis glaucopis, and another lleteronereis form to Nereis Agassizii and Nereis virens. He thinks the Nereids are transformed into Heteronereids at the time of sexual maturity. Claparède states, however, that all the species of Nereis do not have a Heteronereid form, as the species of Nereis far exceed in nuinber those of the so-called genus Heteronereis. He thus concludes: “The fact of animals presenting two sexual forms is not entirely new. The beautiful observations of MM. Leuckart and Mecznikow, and those of M. Schneider on the Ascaris nigrovenosa, have made us acquainted with analogous cases among the Nematodes, where one of the generations, it is true, is hermaphrodite, and the other presents separate sexes. But, among the Acalephs, certain Geryonidæ (Carmarina), according to M. Haeckel, and among the Nematodes, the Leptodera appendiculata, according to M. Claus, present two sexual forms, for each of which gonochorisme' is the rule. The history of the Axolotls, which M. Duméril has acquainted us with, offers certain points of analogy with that of Nereis Dumerilii.

Monstrosities among Infusoria.-Mr. J. G. Tatem has described and figured some very curious examples of the teratology of the Infusoria. Both the account and the figures will be found in the Monthly Microscopical Journal for April. The first figure shows a Trachelias anas, in which the lip, or brow (as it is sometimes called), is inordinately prolonged, somewhat spirally coiled, and clothed with longer and stouter cilia than usual. There is also shown a Chilodon cucullulus, where there is also a monstrous development of the same part, the lip projecting into an elongated proboscis-like appendage, which, as seen waving to and fro, and twisting with every movement of the animal, presented a singularly grotesque appearance. In contrast with the two preceding there is a charming Vorticella. Elegant and attractive as are the several species of Vorticelle, it surpasses them all in beauty, and it is with reluctance only that the author could be brought to regard it as a monstrosity. Met with on several occasions and in widely distant localities, he may fairly question if it may not rather claim the importance of a named variety, under that of Vorticella convallaria, var. monilata.

Wanted Corals to Exchange.—The Museum of Comparative Zoology of Cambridge, United States, is prepared to furnish extensive collections of all the rocks and loose deposits found upon and about the keys and reefs of Florida, also complete collections of the corals, in fresh and well-preserved specimens, in exchange for recent and fossil corals from other parts of the world.

The Australian Mud-fish.Mr. Gerard Krefft has communicated to the Zoological Society a description of a new and very remarkable animal, allied to Lepidosiren, recently discovered in the freshwaters of Queensland. Mr. Krefft considers this animal to be an amphibian, and referred it to the genus Ceratodus of Agassiz, proposing to call it Ceratodus Forsteri, after Mr. Wm. Forster, its discoverer. The figure of the creature shows that it resembles the Lepidosiren very closely.

Curious Malformations in Insects.-Mr. Henry Gillman, of Detroit, Michigan, U.S., records some interesting results of observations conducted in the neighbourhood of the south sbore of Lake Superior.— American Naturalist, March. They refer especially to the dragon-fly. In an individual he specially observed, the skin had just been cast, and the wings, not having yet hardened, were quite soft and delicate to the touch. In one of the wings was a lump-like unexpanded portion reducing the size of the limb nearly one-half. The malformation was similar in each of the instances noticed by him, and was so serious as to prevent the flight of the insect, it invariably falling to the ground on being thrown into the air, and being quite unable to raise itself. A like deformity, with like results, he had previously found to be not uncommon in the Ephemera, which is produced in such countless multitudes in the lake region. The only wonder is that creatures so fragile that almost the touch of a finger injures them should be brought into existence in such myriads, generally unharmed and perfect. He saw two examples of a more singular case of malformation in the beautiful pale green moon-moth (Actias luna). The wing was similarly dwarfed or contracted, a large portion towards the extremity being unexpanded and hardened. The colouring matter and fluids which should have passed down to perfect the development remained above in greenish blisters, protruding the skin of the wing on each side. On breaking this the contents escaped. By pressing those blisters it was possible to project the coloured fluid in any direction within the wing, the motions being quite perceptible in the increased brilliancy of colour of the parts where the fluid passed.

Rotation of the Embryos of the Frog.-In Pflüyer's Archiv (1870, Heft 2 and 3) Herr Schenk describes the movements of the embryo in the ovum of the frog. The rotation which takes place from right to left requires from five to twelve minutes for its accomplishment. He states that it is entirely due to ciliary action—(1) because ciliary cells may be seen with the microscope, (2) because heat increases the rapidity of rotation, and (3) because acids arrest the movement.

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BY PROFESSOR 1. T. ANSTEI), M.A., F.R.S., For. Sec. Geol. Soc.

WITI A GEOLOGICAL MAP AND SEction.

(PLATE LXIV.)

MHE approaching completion of the great tunnel through

1 the Alps, the most interesting and remarkable engineering work-certainly the most daring and speculative workof any that has yet been undertaken for railway purposes, renders an account of its progress and of the condition of the rocks pierced especially interesting. At the present time, more than half the total distance has been completed from the Italian and nearly half on the French, and the rock at both ends being now the same, the structure of the whole mass of mountain penetrated may be estimated with something approaching to certainty. A recent visit by the writer of this article has induced him to believe that an account of the geology of the tunnel rocks would be found to be of general interest. His object will be not so much to describe the numerous and ingenious inventions and mechanical appliances adopted for perforating the rock and ensuring ventilation for the great distance of nearly four miles from each end, as to point out the condition and nature of the rocks pierced in comparison with those seen on the surface. We thus get an insight into the real structure of the Alps at this point, illustrated by a perfect section between seven and eight miles long, obtained by the aid of a tunnel through highly metamorphic rock, the central part being more than 5,000 feet perpendicularly below the actual surface of the ground. Besides the geological structure, several important physical problems will be found to be involved and will receive some explanation."

The part of the Alpine mountain system through which this tunnel is being pierced, is the watershed that separates the waters of the Dora, one of the principal tributaries of the Upper Po, entering the Po at Turin, and those of the Arc, a VOL. IX.- NO. XXXVII.

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tributary of the Isère and ultimately of the Rhone. Crossing the Rhone at Culoz, the railway is carried along the expanded valley forming the lake of Bourget to Chambéry, and thence, in the same direction, without any works of magnitude, but through scenery of very great beauty, till it enters the main valley of the Isère. Proceeding up that valley for a short distance and crossing the river, it turns aside to enter the valley of the Arc, passing Aiguebelle and traversing a narrow strip of granite rock till it reaches St. Jean de Maurienne, a small town in Savoy, celebrated for its numerous and frequent earthquakes, and situated at the extremity of a projection of this granite rock to the east, penetrating the altered jurassic rocks which flank the granite both on the east and west. The rocks here consist of a large series of gypsums and clay, including deposits of iron ore and some veins of galena. A little beyond St. Jean a calcareous rock is crossed, believed to be the representative of the nummulitic series largely developed in southern Europe, and of an age recognised as lowest tertiary. After crossing a long strip of this limestone the jurassic rocks reappear, and beyond St. Michel they are found to be altered and greatly metamorphosed, putting on an aspect so generally characteristic of old rocks, that the geologist not well aceustomed to the Alps and to Alpine geology would be easily deceived by them. A very extensive series of these metamorphosed oolites forms almost the whole mass of the two western divisions of the Alpine system, called the Cottian and the Graian Alps, separated by the valley of the Dora Riparia, and except where interfered with by some patches of serpentine and euphotide, they are remarkably connected and uniform throughout. The tract of country separating France from Italy in this part of Europe affords one of the lowest and most accessible of the numerous passes across the crest or culminating axis of the Alps. This occurs near the Mont Cénis, and over the col or pass known by that name is constructed one of the many magnificent roads for which Europe is indebted to the first Napoleon, who, imitating Hannibal in ancient times, had previously brought his army from France to Italy.

The Mont Cénis pass, though long a difficult and troublesome mountain path, seems to have been known and used from time immemorial. It has only within the present century become a great highway connecting north-western Europe with Italy, and is on the whole well adapted for that purpose, its highest point being only 6,890 feet above the sea. It may be crossed, with comparatively few exceptions, during the whole winter, and it is not so subject to destructive avalanches as many of the passes. The general width between the two principal valleys of the Arc and the Dora is here only twelve English miles, but the

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