the more clear in colour and the more definitely banded, the markings of arbustorum are, on the other hand, more mottled and less definite. Although H. nemoralis is so globular as not easily to be confounded with other species, its colours are so varied that scientifically there might be formed a whole catalogue of its sub-varieties worthy of distinction. One species, for example, is yellow with dark brown rim; another brown, but banded on tints of white, yellow, or brown; another greenish-yellow, with three narrow brown bands; another, with five broad belts, darker and wider in different places; another, pink with four bands, the three lower dark redbrown; another, brownish-pink, with one broad belt occupying nearly the whole whorl, and a second narrow band above it; and another pink, with five pale brown bands. These, the more common variations, are by no means a complete enumeration of the varieties of colour. Sowerby makes the curious assertion that this wood snail will eat earthworms or even cooked meat, and we dare say it would if it could get the chance. It is in its turn infested with a parasitic insect. In dry weather not a specimen of it is to be seen. An hour after a shower you may count perhaps thousands in the woodlands. In cold, too, it retires, as already hinted, into private life, amongst grass-roots and rubbish. Much discussion has ensued on double glazing in certain contemporaries weighted with the responsibility of our domestic comfort. Let them take a lesson from the snail. In winter it closes over the mouth of its shell, not only with an outer semi-transparent mucous covering, but afterwards retiring further inwards, it protects itself by means of a second film, securing a warm stratum of air betwixt it and the outer cold for the entire duration of its four months' fast.

The shell of H. hortensis, the garden snail (fig. 180), again, is always about one-third smaller, and it is a little more globular still than H. nemoralis (fig. 176). The eggs of H. hortensis resemble small peas, and a bad kind they would be for the gardener to sow. Macgillivray (to whom I shall again refer) notices three varieties of garden snail: the Common Banded; the Unicolor (not banded); the Arenicola (sand-inhabiting).

The peculiarity of this last variety is a strange one-it is a smell. Has any one ever smelt a snail which emits an odour of onions? It was either this variety of the garden snail or the onion snail (Zonites alliaria) altogether; and this garlicscented odour, as it is more properly called, remains perceptible even after the creature has been killed in hot water. [Collectors will understand why we kill snails thus—it is to get quit of the inhabitant at once; and to preserve the enamel of the shell, the scalded one must instantly be dropped from the hot into cold water.]

Linnæus, whose original arrangement of molluscs

was successively upset by the new classifications of Lamarck, De Ferussac, and Bosc, and entirely abandoned at the dictation of Dr. Oken, included in the genus Helia many fresh-water, fluviatile (river), and even sea species. But so limited has been the view adopted by more modern authorities, that Professor Macgillivray, labouring, it is true, under the restraints of a northern clime (Aberdeenshire), although known as one of our most diligent collectors (he was naturalist to the present Royal family, and the late Prince Consort is understood to have acquired the copyright of his works), adduces, besides the three Helices already mentioned, only the following, treating all the minor specimens, not as Helices, but as Zonites :-The Wrinkled Snail, Helix caperata (fig. 181); the Bristly Snail, H. hispida (fig. 182); the Scaly Snail, H. lamellata (fig. 183); the Prickly Snail, H. aculeata (fig. 184); and the Little White Snail, H. pulchella (fig. 185).

PWAI-NGYET.

I HAVE noticed your remarks on the substance

called Pwai-ngyet in your interesting little periodical SCIENCE GOSSIP. As it was I who furnished the bees which were forwarded by the Agri-Horticultural Society of Calcutta to Mr. F. Smith, of the British Museum, for identification, and which he pronounced to be Trigona læviceps (as Dr. Mason, to whom you refer, states in his book on the natural productions of the Tenasserim provinces); and as, therefore, I know both the substance and the insect well, I have great pleasure in giving you such information as I can on the subject.

A few years ago, the secretary of the Calcutta Agri-Horticultural Society wrote to me for information regarding Pwai-ngyet. Until then, I knew very little about it; but my attention having been called in this way to it, I made it my business to find out what it was.

If I read your remarks rightly, you appear to be of opinion that Puai-ngyet is the pure unaltered gum or resin of Canarium strictum, only bored and channelled by the bee. If this were so, then the substance should only be found on that tree. It is, however, found on different trees: sometimes too in the ground, or in a hollow among rocks; and, occasionally, even in the hollow post of an old house. I have seen the bees making their nest in all these several situations.

Pwai-ngyet, I believe myself, is a combination of various gums or resins, and probably also of oils, gathered from various sources, while in a soft state, by the bee, and built up and moulded, very much as wax is moulded; with this difference, that whereas wax is formed by the honey-bee into cells of perfect and uniform symmetry, the cells in Pwai-ngyet assume no regular form at all.

What trees contribute their juices to form Pwaingyet I cannot say for certain, though I incline to think that Thengan-tsee, or the resin of the Thengan (Hopea odorata), is the chief ingredient, and that the oil of the various Dipterocarps, or wood-oil trees, particularly of Dipterocarpus lævis, the wood-oil tree par excellence, also enters into the composition of the material. My reasons for thinking so are, that the texture, the colour, and the smell of Pwai-ngyet are all such as would apparently result from a combination of the two substances mentioned; and, that Hopea odorata and Dipterocarpus lævis are among the principal giants of our forests, and common trees. On the other hand, I do not think (though I will not be sure) that Canarium strictum is found in our provinces, although I believe a species of Canarium, a large timber tree, is found in Pegu.

The Trigona læviceps builds its nest generally in

the hollow of a tree, entering by a small aperture." These apertures are lined with Pwai-ngyet, and sometimes only show a small rim of that substance raised above the bark of the tree. Sometimes, however (perhaps always if undisturbed), the bees go on building outside and adding on to the rim, until they have formed a wide-mouthed entrance which projects as much as a foot from the tree. These

Fig. 195a.Front view of Mouth.

structures commonly assume the shape of the mouth of a large trumpet flattened horizontally, and have a perpendicular diameter of a foot or so, and a horizontal diameter of three or four inches. They are built with great regularity in their exterior half, but not so regularly towards the base, from the necessity of adapting the structure to the shape of the tree where the hole may chance to be. They are very curious and pretty objects, but being very prominent, attract the notice of the passer-by, and so often lead to the spoiling of the habitation.

"Sic non vobis nidificatis apes." I send you a rude sketch of one of these trumpet-openings. I despatch also, by post, together with this notice, a small piece of Pwai

Fig. 1956. Nest of Trigona laviceps, one-sixth natural size.

ngyet, broken off the upper base of such a work. By holding this up to the light, you will see three or four large cells of about an inch in diameter, with

* The insect was figured in SCIENCE GOSSIP, vol. I. p. 252, fig. 3.

out any opening. I can only suppose that the object of these cell-walls is to strengthen the narrow base in its support of the larger projecting mass. If so, here is another instance of a mysterious intelligence possessed by one of the smallest of living creatures.

This piece, marked No. 1, will show the ordinary texture, colour, and general appearance of Pwaingyet, as it is found in the jungles. No. 2 is nearly white, a very unusual colour. I send it because of its greater resemblance to Thengan-tsee, or the resin of the Hopea odorata; of which I also send a small piece (No. 3), in order that you may be able to ascertain how far the two substances are chemically identical.

What the internal economy of the nest of Trigona læviceps is I cannot say, as the tree has commonly to be felled in order to obtain the contents, and this I have never seen done. I am informed by the Burmese that from five to ten viss are usually obtained from one nest. A viss is about 3 lb., and costs about 4 annas (6d.) in the Bazaar. I should imagine that, considering the source whence it is procured, the supply must be very limited; and, if exported, it would soon equal beeswax in price.

Its principal, if not only use, at present, is for caulking; and, for this purpose, it is mixed with earth-oil, or petroleum.

The method is to boil the Puai-ngyet in water, which makes it quite soft, and then to knead it with a certain quantity of the petroleum, until it attains the consistency of a lump of putty, which it much resembles. In that state it is fit for use, and is extremely viscid and tenacious. On putting a piece of Pwai-ngyet into boiling water, in order to perform the operation myself, I noticed that the surface of the water was covered with a thin film of oil. This confirms me in the idea that oil is united with resin in the composition of Pwai-ngyet. It is soluble in oils and in turpentine, but not in spirits of wine. I may conclude by mentioning that the mistakes made by several persons in Burmah with regard to the origin of this substance must have arisen from the fact that the name of Pwai-ngyet is often used here, in the bazaars, to denote any kind of resin or Dammer, but the true Pwai-ngyet of the Burmese is that made by the small bee called Trigona læviceps, and is made by them in the manner I have tried to describe.

some such excrescence of the trunk as I have tried to represent. The actual entrance into the tree in this instance was by a narrow perpendicular slit, two and a half inches long and three-tenths of an inch wide, the upper part of which may be seen in the specimen. The width, laterally, in the middle of the stem of the structure, is exactly one and a half inch. The weight of the whole, judging by the portion I have, may have been half a pound.

C. P.

THE LITTLE BITTERN (Ardea minuta).

THE

HE student-lover of the natural history of our country always feels, as each fresh phenomenon is brought under his notice, a new interest given to his pursuits, an additional stimulus to his exertions. Whether the discovered object be common or rare is at first of little import, so long as it possesses the merit of being new. But, perhaps, after consulting his books, or his more learned companions, our friend finds that what is fresh to him is by no means unknown to the world at large; and then, although he cannot altogether ignore the delight which he has already experienced, he may feel that it has been thrown away upon a comparatively unworthy object. Suppose, however, on the other hand, that his "find" should be really interesting, not merely to the novice who has obtained it, but to the scientific community generally, we cannot but admit that there is a certain feeling of pleasure connected with it, which is renewed as often as the object is contemplated. We may well suppose that this feeling is experienced in no ordinary degree by the few favoured individuals to whose lot it falls to obtain a specimen of the bird whose portrait stands opposite-the Little Bittern (Ardea minuta).

The earliest mention of the Little Bittern as a British bird occurs in a valuable old work, perhaps less known than it deserves, and published in 1667Christopher Merrett's "Pinax Rerum Naturalium Brittanicarum." In this book, immediately succeeding the mention of Ardea stellaris-the Bittourn," comes the following:-"Ardea minor, quam ad me transmisit Dr. Jenner, ex agro Wiltoniensi." Of course, in those bygone days, when observers were few, and books on natural history fewer, we could not expect to find the Little Bittern an object of much observation; and it is not until 1808 that it is mentioned by Montagu as having been noticed "contiguous to the river Credey, in Devonshire," where three specimens were shot. The county of Norfolk appears to have produced several examples; in 1826, a young specimen was shot on the banks of the Thames near Windsor, which Yarrell remarks, "was believed to have been bred there, from the situation being

favourable, and the circumstance of a second bird in the same state of plumage being seen about the same spot for several days at that time." Specimens, but seldom more than two or three, have been obtained, at various dates, from the counties of Devon, Cornwall, Dorset, Hants, Somerset, Berks, Middlesex, Salop, York, and Northumberland; also from North Wales, from the east and south of Ireland, and from the Orkney Islands. We have recently heard of a specimen obtained near Deal. The specimen figured was shot by Mr. Thomas Marshall, of High Wycombe, at the

latter end of last year: it was killed as it flew from a well-known island in the river Thames, called Queen's Ait, about halfway between Maidenhead and Windsor, and just within the confines of the county of Bucks: the island is said to be admirably adapted for its nidification. At about the same time another specimen was shot at Christchurch, Hants, by Mr. Hart; in which locality the Little Bittern had previously occurred.

There is, we believe, no recorded instance of an egg of the Little Bittern having been obtained in Britain. Mr. R. B. Sharpe, indeed, recently mentioned, in the "Naturalist" that he had received a genuine specimen from Norfolk, and was kind enough to offer it for our inspection; but the results of further investigation are very unsatisfactory, and

it seems doubtful whether the egg has any claim to be considered British, Mr. Sharpe having, apparently, been much deceived on the subject. Mr.

Ν

POISON-FANGS OF SPIDERS.

same periodical that the bird occurs in Norfolk only "as a rare straggler:" he also states that he "never heard of its nesting, the birds being invariably shot on their first arrival." The Rev. F. O. Morris, in his "Nests and Eggs of British Birds," states that the eggs vary in number from four to six, "and are of a pale whitish-green colour."

The general appearance of the Little Bittern is very striking. The head is somewhat large in proportion to the body, and is surmounted by a black crest. The general hue of the feathers is a rich sienna-brown, with black and white markings: the legs and feet are yellowish-green. The long neck and beak, and peculiar head, show its relationship to the Common Bittern (4. stellaris). The bird does not measure more than eighteen inches from top to toe, and its weight is remarkably trifling. When flying, the bird much resembles a woodcock; and was at first considered as such, both by Mr. Marshall and Mr. Hart. It occurs in Sweden, Germany, Holland, France, and Italy, as well as in various of the islands of the Mediterranean. Asia also produces it; and it is mentioned as having been observed in Africa by recent travellers. The reclaiming of our various fen-districts may have resulted in the extermination of the Little Bittern from localities where it may formerly have been abundant; in which case it is not the only treasure which nature has lost while yielding to art.

Bewick's information about the Little Bittern is very scanty, but his figure of it may be preferred to that of Yarrell. For further information regarding this species, as well as for a figure and technical description, reference may be made to Yarrell, Macgillivray, or the Rev F. O. Morris's Birds of Great Britain."

* * * 串 * *

B.

THE IMPORTANCE OF DEFINITE PRINCIPLES.More bones enter into the formation of the skull in fishes than in any other animals; and the composition of this skull has been rightly deemed the most difficult problem in comparative anatomy. "It is truly remarkable," writes the gifted Oken, tc whom we owe the first clue to its solution, "what it costs to solve any one problem in philosophical anatomy. Without knowing the what, the how, and the why, one may stand, not for hours or days, but weeks, before a fish's skull, and our contemplation will be little more than a vacant stare at its complex stalactitic form."-Professor Owen's "Principal Forms of the Skeleton."

BOTANICAL MEM.-Why is Opium like a truthful father? Because it is Papa-veraceous.-Fun.

or two "little facts" relative to this subject. May I trouble you with the following:

Nearly 200 years ago, Leeuwenhoek alluding to this fact of the spider, describes it as follows:-" And in each of these fangs (for so I will call them) is a small aperture, through which, in all probability, a

liquid poison is emitted by the spider at the time it inflicts the wound ;" and he gives the above diagram (fig. 197). This representation is that of a fang "as seen through the microscope;" and he says further:-"At i is to be seen the small aperture I have mentioned, which aperture appears the same on both sides of each fang, and through this we may reasonably conclude the spider ejects its venom."

In the History of British Spiders lately published by the Ray Society (a work which some of your correspondents would do well to consult before writing to you), Mr. Blackwall states, "The fang is very hard, curved, acute, and has a small fissure near the point, which emits a colourless fluid secreted by a gland."

But the presence of these small openings in the fangs of a spider may be still more satisfactorily proved by any one who has a moderate microscope; he must, however, examine the inner surface of the fang, which is towards the mouth, and view it as an opaque object with the lieberkuhn. I have never seen the opening on the outer surface of the fang, and the fact of Leeuwenhoek remarking that the "aperture appears the same on both sides of each fang " might incline one to believe that he never saw it at all; but no one can hold such an opinion after examining the exact drawing he gives. Neverthe