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10° to the left of Capella); from thence it glided slowly across the sky, shining with a brilliant green light, and exhibiting a pearshaped disc of one-third of the apparent diameter of the full moon. When it had arrived at the middle of its path (being almost due north), its velocity abated, and its colour changed to a whitish-blue. The meteor, accompanied by a diminutive red tail, and followed by a train of sparks, then regained its original velocity, and gradually approaching the horizon, eventually disappeared behind a cloud lying parallel, and close to the horizon in the N.N.W. The whole time occupied during its flight being 2'5". In my letter reporting the auroral display of Nov. 10 last year, I suggested the application of Photography to the solution of auroral problems; might I venture to ask if any of your photographic correspondents have been able, during the displays of this year, to prove the possibility of taking auroral photos? I think the results would be interesting to most of your Leaders. ROBERT MCCLURE

Glasgow, Nov. 4

ON Wednesday night the 6th November, whilst looking from this place over the sea, directly west, a few minutes before ten o'clock, I saw a meteor of large size subtending I should think one-sixth the angular magnitude of the moon. It was accompanied by a short scintillating train, and moved slowly quite parallel with the horizon directly north. Its elevation was about 15°, and its rate of motion I should think 11° per second. The night was dark and somewhat cloudy, and the line described by the meteor seemingly quite straight. Blackpool, Nov. 8

Day Aurora

D. WINSTANLEY

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Waikanae (on the north side of Cook's Strait) it is excessively abundant. From Waikanae to Horowhenua it is comparatively scarce; but at the latter place, and for a few miles farther north, it is said to be abundant. At miles, it is very rare. At the mouth of the Wanganui Manawatu, and thence along the coast for twenty or thirty river, again, it is very abundant; and a story is still current among the natives of the district about a fishing party, all of whom were bitten by this dreaded spider, and in two cases with fatal results.

The writer then adduces several instances to prove that the bite of the spider is occasionally fatal, and certainly very painful and distressing. But, he says, "I have satisfied myself that, in common with many other venomous creatures, it only exerts its dreaded power as a means of defence, or when greatly irritated; for I have observed that on being touched with the finger it instantly folds its legs, rolls over on its back, and simulates death, remaining perfectly motionless till further molested, when it attempts to escape, only using its fangs as the dernier

ressort!"

The cocoon or nest of the katipo is perfectly spherical in shape, opaque, yellowish white, and composed of a silky web of very fine texture. The eggs are of the size of mustard seed, perfectly round, and of a transparent purplish red. They are agglutinated together in the form of a ball, and are placed in the centre of the cocoon, the exterior surface of which is sometimes encrusted with sand. The spider itself undergoes the following changes in its progress towards maturity :-In the very young state it has its body white, with two linear series of connected black spots, and an intermediate line of pale red; under parts brown; legs light brown, with black joints. In the next stage, the fore part of the body is yellow, with two black" eye spots;" sides black, with transverse marks of yellowish white; dorsal stripe bright red, commencing higher up than in the adult, and with the edges serrated. At a more advanced age the stripe on the back is brighter, with a narrow border of yellow, and the thorax and legs are nearly black. In the fully adult condition, the female of this spider is very handsome both in form and colour. Examples differ considerably in size, the body, which is

THE KATIPO OR VENOMOUS SPIDER OF almost spherical, varying in development from the size of

FR

NEW ZEALAND

ROM the interesting "Field Notes of a Naturalist in New Zealand," which have been appearing in the Field for some weeks, we extract the following description of this hitherto little-known animal.

Among the invertebrata there is a venomous spider known as the "katipo ;" and, as this is almost the only noxious inhabitant of the land, it may be interesting to give some account of it, especially as there are some very curious points in its natural history. The first scientific notice of the existence of a poisonous spider in New Zealand was furnished by Dr. Ralph, in a communication to the Linnean Society in 1856 (see Journal Proc. Lin. Soc., vol. i., 1856, pp. 1, 2). Dr. Ralph's paper contained a short description of the full-grown spider, observations on its nesting habits, and an account of experiments which he had made in order to test the potency of its venom. The native name, katipo, signifies "night stinger" (being derived from two words, kakati, to sting, and po, the night), and, although more strictly applicable to the venomous spider, it is often used to denote a wasp or other stinging insect. The species has been described and figured in the Transactions of the New Zealand Institute (1870, vol. iii. pp. 56-59), under the name of Letrodectus katipo, and is closely allied to, if not identical with, one inhabiting Australia. The exact range of this spider in New Zealand has not been accurately ascertained; but it appears to be rather local in its distribution, while its habitat is strictly confined to the sand hills skirting the sea-shore. Along the coast from Wainui to

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a pigeon-shot to that of a small green pea; and in the largest specimens the outspread legs, measuring across, cover a space of only three-quarters of an inch; thorax and body shining, satiny black; a stripe of bright orangered passes down the centre of the body, the edges being tinged with yellow. At the anterior extremity this stripe is broad and angular, and is surmounted by an open narrow mark of white in the form of a nail head; below this, and immediately above the junction of the thorax, there are two divergent spots of orpiment yellow, with white edges; legs black, with the extremities inclining to brown. The male is considerably smaller, and has the body shining blackish-brown, with an obscure narrow line of yellow down the centre of the back, broader towards the posterior extremity, and a similar interrupted line on each side of the body.

The spider here described belongs to a genus which contains several species in other parts of the world, also reputed venomous. Walckenaër, writing of the Latrodectus malmignatus, an allied species, common in Sardinia, Corsica, and parts of Italy, remarks :-"This spider is certainly poisonous; its bite causes, they say, in man pain, lethargy, and sometimes fever ;" and Mr. Abbot, in his account of Latrodectus in his "Georgian Spiders," states that its bite is "undoubtedly venomous." curious, also, as already noticed by Dr. Powell, that the species of this genus, so widely distributed over the world as to be found in Europe, America, Australia, and New Zealand, should all agree in being black with red markings, for colour is of all characteristics the most variable, and especially so in the case of spiders.

It is

30

INSECT METAMORPHOSIS*

Great

EVERYBODY, whether learned or unlearned, is aware that
insects undergo changes in their shapes and habits.
numbers of popular works on natural history have made the
description of these changes or metamorphoses familiar to the
public; and Newport, Dugés, Heroldt, Fabre, and those British
entomologists and naturalists whose names are household words
amongst us, have informed the scientific world upon the ana-
tomical and minute changes of structure which accompany the
The array of
wonderful varieties in form and in method of life.
facts is enormous, and yet, with all this vast amount of sterling
knowledge to build upon, very little progress has been made
towards recognising the cause and meaning of metamorphosis in
biology-in the science of life. The facts and details of the sub-
ject have been accumulating, but the nature of its philosophy
has been studied by very few naturalists, and it is only of late
years that Lubbock and Fritz Müller, and a few others, have
been stimulated by the light of the theory of evolution to ex-

amine into it. Believing that the subject is increasing in interest, and that its consideration bears upon some of the most im. portant theories respecting life, it is proposed to devote this lec ture to a description of the different kinds of metamorphoses in insects, and to a consideration of the biological meaning of the phenomena.

Let me recall to your recollection two instances of what When may be called perfect and complete metamorphoses. the tenderest cabbages are growing in the early summer, a number of very small caterpillars or larvae may be seen upoa the plants, devouring them in a regular and systematic manner. Avoiding the leaf-veins as indigestible, they nibble the juicy leaf, and consume daily more than their own weight. These pests of the gardener have small heads and ends, and the body is greenish and striped with yellow bands, being at the same time hairy. At first very small in size, the caterpillars do not attract much attention, and especially, as after living for a few days, they hide After a short up out of the light, and look shrivelled and ill. time, the caterpillar in retreat bends its back violently, and

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splits the skin of one of the rings or segments of the part nearest the head, then a vigorous struggle enables the legs and the head to be withdrawn through the crack, and the larva is noticed to have attained a new skin within the old one. It crawls on to its favourite plant and makes up for lost time, grows rapidly, and really may be said to live to eat. It cares not for its fellows, nor for any other leaves; it is content with its own cabbage, and has no ambition and no desire to quarrel or to move away. During growth the powers of mastication and of digestion increase, but they are checked several times by the larva having to pass a period of quietude whilst a new skin is finished under the old, and whilst this is cast off. These skin sheddings have a definite relation to the increasing size of the insect, but they are not simple changes of skin because the old one has become too tight for its rapidly growing possessor. They accompany certain important changes within the insect, and not only is the outside skin shed, but the mucous membrane of the digestive organs A Lecture delivered before the British Association, 1872, by Prof. Duncan, F.R.S.

and of the air tubes which enable the creature to breathe, suffer also. They are really important elements in the metamorphosis, which term includes the sum of the changes of shape, habit, and instinct.

When full growth has been attained, the caterpillar crawls from its cabbage and wanders restlessly about, even to con siderable distances, in search of a dry sheltered spot. After having discovered such a locality, it fills up the space between its hind legs with silk, and attaches this part of the body to the wood or stone, as the case may be. The larva then hangs head downwards, and forthwith begins to bend its head backwards, upwards, and then from side to side, until, after a little practice, it is enabled to touch the solid substance to which it is hanging on either side of its body. Then some silk is secreted, and by applying the mouth to the spots touched one after the other, fine sling of silk thread binds the insect down and prevents it from being swayed to and fro by the wind. This is the last act of the larva which shows any evidence of will. Then it begins to look shrivelled, shorter than before, and broader behind the

head, and after a time the skin splits, and is shed with greater or less wriggling. A sticky, varnish-looking moisture covers the very different-looking thing which now presents itself, and dries rapidly, and forms a case over the skin of the "pupa" beneath. The alterations within and without the insect at this time, that is to say, during three or four days after leaving the cabbage, are carried out with great rapidity, and the future butterfly is well foreshadowed at this period in the structure of the chrysalis or pupa. Hanging as a chrysalis or pupa in a perfectly immobile condition, neither seeing, hearing, nor tasting, and losing very little weight from the exhalation of its moisture, the insect lives on for many months, and until spring has nearly ended. Then the dark case splits, and a tender white butterfly crawls forth, and, under the influence of warmth and the sun, becomes dry,

is large enough to admit the wasp's body, the legs remove, by a process of brushing, the particles loosened by the jaws. After a short time the wasp will be found to have made a tunnel, and the constant out-pour of sand and clay indicates that excavation is still proceeding out of sight.

Soon the Odynerus perfects two or three chambers deep in the bank and opening into the tunnel. She (for it is the female who does the work) carefully pounds the insides of the cavities and removes all roughness from them, and leaves them as commodious hollows, water-tight, and not likely to fall in. This is not all. On coming back into the light, the wasp seizes cylindrical pieces of earth, and moulds them more or less into shape with her jaws, and places them in front of each other, and side by side, so as to form a hollow tube, which sticks out from the bank and opens into the tunnel. The free end of this ante-chamber is left open, and the pieces of which the whole is formed are gummed together and pressed. The tube is ex

[graphic]

FIG. 2.-Esophageal Epithelium.

stretches, and unfolds its crumpled-up wings, walks feebly upon long legs, trails a short body, moves a curious flexible trunk in front of its head, the result of the modification of its former jaws, and takes to flight. The common white butterfly, whose solitary flight is so zigzag and wandering, and whose flight in company is so tumultuous, ascending and vibrating, lives for love. It has a soul above cabbages, and rarely condescends even to sip or suck the daintiest nectar from flowers. After a longer or shorter existence, it begins to lay eggs, and places them in the immediate

FIG. 3.-Stomach Structure.

neighbourhood of the favourite food of the larvae, which are to come from them.

Another familiar example of perfect metamorphosis may be studied in the instance of one of the false wasps, Odynerus parietum. This small wasp-like insect may be seen on the other side of the Channel in great companies on lucern and clover when in full flower. It is a solitary kind, and the male and female care nothing for their companions, who rush and tumble over, in, and about the flowers, sucking their sweetness, and squabbling

FIG. 5.-Stomach Structure of Pupa.

tremely fragile, and the pieces of it are not in contact everywhere. Nevertheless, the Odynerus passes along it readily enough, but no other insect of its size can do so. All this work is carried on whilst the wasp appears to be in an intense state of excitement, and when it is completed the insect flies off to the flowers again. But not to return to its former habits. On the contrary, the purposeless tumbling about of flowers, and the occasional sip of nectar, are forgotten, and the flighty little vegetarian becomes a ferocious and ardent huntress of prey. She seeks the small larvæ of a species of weevil which abounds about the plants, and seizing one, digs her sting into it, so that a weak venom is introduced close to the nervous system of the victim. The larva is paralysed

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and flying for the freshest corollas. Day after day this buzzing busy crowd may be seen leading a life of happy enjoyment, feeding, playing, and flirting; but after a while an unusual excitement is noticed amongst a large number of the insects. These extend their flight beyond the favourite field, and seek the neighbourhood of sandy clayey banks close by. They may be observed digging their heads into the sand with great assiduity, and pulling out sand grains, and gradually forming a hole. Each wasp works independently of its neighbour. As soon as the hole

FIG. 6.-Stomach Structure of Imago.

at once, but not killed; on the contrary, it remains motionless, but lives. She then flies off with her prey to the bank, enters the tubular ante-chamber, traverses the tunnel, and reaches one of the chambers. Here she deposits her insensible victim, and lays one egg close to it. Returning again to the field, she seizes another larva, stings it, and carries it off to deposit it close to the first. This procedure is repeated as many as thirty times, and the chamber becomes full of insensible weevil larvæ and one Odynerus egg. The other chambers are filled in the same manner, and an egg is laid in each. Then the wasp comes out of the tunnel for the last time, breaks down the tubular ante-chamber, so as to hide the entrance to the tunnel and chambers, flies off, and dies. She never sees her offspring, for which she, a vege tarian, has provided animal food in abundance.

The egg is soon hatched in each chamber, and a small, legless, and extremely delicate larva crawls forth, and seizes upon the victim close to it. So tender is the larva that the least roughness of the sides of the chamber would destroy it, and the least struggle on the part of the poisoned weevil grubs would kill it; but all this has been made safe, and the little thing eats into its living prey, and when one is finished it attacks another, until all are eaten up. This is the life of the larva. It is incapable of walking any distance, and simply leads a life of gormandising on the flesh and juices of weevil grubs. It never emerges from the chamber, and when it has no more to eat, spins a cocoon of silk around itself, and sleeps therein during the late autumn, the winter, and until the spring. Then a change in form ensues, and a pupa, which greatly resembles the perfect insect, appears under the skin which is shed. In the course of a few weeks the perfect false wasp escapes from the pupa skin, digs its way into the world, and emerges to enjoy the destiny already described.

Many other false wasps which belong to the same group of insects as this Odynerus have a somewhat corresponding life cycle, and choose many curious kinds of prey, but the formation of the safeguard of the tubular ante-chamber places this kind in advance of all others. It is then an example of very perfect metamorphosis with high instinct, and, like in all other instances of what is termed perfect metamorphosis, there is an intermediate stage of a quiescent pupa between that of the larva and imago, both of which are able to lead independent and distinct kinds of lives, and to take food.

Considered as isolated examples, these two instances of metamorphosis are perfectly inexplicable, except on the theory that the successive changes-shape, structure, and habitwere especially given to the species at their origin, by special creation. When, however, the nature of the very different metamorphoses of other insects, which closely resemble these in structure, is examined into, this view does not give entire satisfaction, and an uncomfortable feeling arises, that we with finite understandings are tying down the operations and mysterious ways of Omnipotence to our own limited standard.

But before proceeding any further, it is necessary that the nature of some of the structural alterations which occur during metamorphosis should be stated. By so doing a distinction can be appreciated between ordinary continuous growth or progressive development, and the changes which occur during the perfect metamorphosis of an insect. Consider shortly the nature of the change of outside form. A young larva of a butterfly or moth has a head which is not separated by a neck from the long body, and the whole is divided more or less distinctly into rings or segments. The three segments next to the head form the chest and support the true legs, and are succeeded by nine others belonging to the body or abdomen. There are then thirteen in all. The body segments are nearly equal, but the last is the smallest, and it, together with some of the other rings, supports what are termed false legs or claspers. They are continuations of the skin, and do not exist in all larvæ of butterflies and moths; and, although they are extremely useful in enabling the insect to hold on and to crawl, they disappear in the pupa state with the last skin-shedding. Thus there is the head segment, and three chest segments, and nine body segments, and on the side of each of these, excepting the head, is a point, which usually marks an opening where air tubes or trachea enter the body to ramify over the whole of the internal structures. When within the egg, and before it was perfectly formed, the head of the larva consisted of at least four separate pieces, but these united and coalesced in one before birth. None were destroyed, but the edges of the separate portions fused together. A corresponding fusion and blending of certain of the chest and body segments occurs during metamorphosis, and there is neither a destruction nor new creation of parts to produce the extraordinary difference between the long body of a caterpillar, the short swathed figure of the pupa, and the great chest and small abdomen of the butterfly. The same anatomical elements are present, but they are more or less modified.

The first skin sheddings of the caterpillar do not add to or alter its segments, but the last skin shedding which occurs during a period of immense internal change exposes the pupa or chrysalis to view, and all the characteristics of the skin of the larva are lost. On commencing this last skin shedding, the chest segments, 2, 3, and 4 (Fig. 1) of the caterpillar, increase in size, and the insect really soon begins to shorten. The small Tortoise-shell butterfly larva is thus suspended, with its skin on, for some ten or twenty hours before the chrysalis is revealed.

During this time, the 2, 3, 4, and 5 segments become much enlarged and curved downwards by the action of the muscles of their under surface, which are repeatedly contracted and expanded slowly. The skin bursts, and the insect then exerts itself to the utmost to extend the fissure along the segments of the body, and gradually draws out its antenne, or feelers, and its weak but long legs, and immature wings, all of which have been maturing beneath the old skin, and are covered with an extremely delicate tissue. The false legs drop off with the old skin, and the pupa hangs in this moist and curious condition for a few minutes. Then it makes a few powerful efforts, and com tracts and expands itself to the utmost by taking in air through its air tubes and forcing it out again by bringing the segments closer together. The result is to contract the body segment: along their under surface, and to diminish their length generally. The front margin of one segment is drawn up within the hinder edge of the one in front, and especially in the case of the fifth and sixth segments. This contraction persists, and in the neighbour hood of the fifth is sufficient to initiate the small waist-like circular division between the chest and the body, which becomes more dis tinct in the imago than in the pupa. Atrophy and shortening of the fifth and sixth segments occur; and there are correspond ing changes in the first and second segments, so as to commence a neck. A gelatinous viscid fluid is secreted by the pupa, and covers all its delicate external skin, and by hardening agglutnates all beneath. After a while the true skin of the pupa, is found separated by air from the dark pupa case outside. After the escape of the imago from the pupa case, if its wings le removed, and its head, chest, and body be examined, the distinction between the number of its segments and those of the full-growr larva will be readily appreciated. The nine body-rings of the caterpillar exist, but are much modified. The two terminal se drawn up inside the body, and the first segment has joined itsent to the last chest-piece. The shortening is very great, whilst the enlargement of the rings which support the wings-namely, the third and fourth-with much consolidation and fusion of them, does not compensate for it. As may be supposed, the shortening of the internal organs must be extraordinary, and as a matter fact the nervous cord is shortened, its ganglia are concentrate, and the digestive apparatus is diminished in length in a remark able manner.

The changes in the digestive organs keep pace with thes of the skin and general shape, and may be briefly described as follows:-When a caterpillar nips off a piece of a leat with its jaws, the morsel is passed into the gullet, which is a short tube leading to the stomach. The gullet is composed of 2 mucous coat which is internal, and of a muscular covering wha is external. The mucous coat consists of a delicate structureless membrane, which is continuous with a corresponding tissi in the mouth in front and in the stomach behind. It is called the basement membrane, and that of the gullet is folded longway'ı, when it is empty. When the gullet is crammed with food, the folds are obliterated and the membrane is stretched. All the aside of this membrane is covered with a layer of delicate boxagonal cells, which are very small and thin, and consist of a plat cell wall and transparent fluid contents (Fig. 2). They cover the basement tissue like a pavement, and the morsel of food comes in contact with them, and they absorb and transmit any vegetalle liquids which may escape from the cells of the leaf. Betwe the hexagonal pavement cells here and there are oval depression filled with granular mucus. The basement tissue is slightly d pressed in these spots, and these crypts secrete a fluid whicks like the salivary glands of man upon starchy and sugary flui ́s Amongst the hexagonal cells are others which have their up surface produced into a short tooth-like projection, that are shadows a remarkable structure in the perfect insect. Quise the basement membrane is a single row of hoop-shaped muscula. fibres. They are broad and nucleated, but not striated. Fack fibre encircles the gullet, and tends, with the simultaneous cuttraction of its fellows, to diminish the calibre of the tube, and to throw it into longitudinal folds. Their passive dilatation, in the contrary, permits the gullet to become distended. have, however, the peculiarity so common in the circular musculat fibres of all animals, of contracting one after the other in scheand of dilating or expanding in the same rhythmical manner. Th result of this progressive contraction is to force the content the gullet in the direction of the stomach. The alterations d contraction and the expansion permit the layer of muscular blac which is outside the circular set, and whose direction is longitu dinal, to pull up and shorten the canal. The long fibres are

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attached to a ring behind the mouth, and around the commencement of the gullet, and they are continued down the tube to the stomach. They are closely packed, and are very distinct. When the gullet is shortened by their contraction, any food in it is rought nearer the opening into the stomach, and then it is forced nto that organ by the progressive contractions of the circular fibres. The piece of leaf is lubricated by the granular mucus of he crypts, and is squeezed by the contraction of the circular ibres. Much of the contents of the cells of the leaf is thus set free, and is absorbed by the mucous cells, and transmitted through the basement tissue to the blood, which permeates all the tissues more or less.

The stomach is large in comparison with the size of the larva, is cylindrical in shape, and does not taper gradually into the gullet in front and the intestine behind. The calibre is many times greater than that of the rest of the digestive canal. Like the gullet, a mucous layer, a basement membrane, and two sets of muscular fibres, enter into its composition. But the mucous membrane differs in every particular, except in the structureless basement membrane. The basement membrane is densely covered internally by an aggregation of large cells of two kinds, and the more active the larva may be in its eating, the more numerous and larger are these cells. One kind is elongate, and narrow at the base, where there is an attachment to the membrane, and rounded at the free end (Fig 3). They are thus more or less club-shaped, and they are formed by a very delicate cell wall, a nucleus and more or less granular, coloured, and liquid cell contents. They are crowded together, and belong to what is called 'columnar epithelium. They become less bulky, thinner, and crooked, if the caterpillar is starved, and just before the skin-sheddings also. Another kind is represented by large globular cells, which are fewer in number compared to the others. They are composed of a very delicate cell wall, of nuclei, and liquid contents, and they burst in the ordinary process of digestion, and appear to supply a gastric juice. The columnar cells, on the contrary, absorb nutritious matters, and transmit them through the basement tissue. These huge cells are very remarkable, and all degenerate, and greater part are cast off during skin-sheddings. A layer of circular or hoop-shaped muscular fibres is found outside the basement membrane, and whilst those of the fore part of the stomach are so closely applied to each other, side by side, as to form a continuous circular muscular coat, those of the nether parts of the organ are wider apart, but at the termination of the canal in the intestine they are again concentrated, and not simply in one row, but in many, so as to form a dense circular muscle or sphincter. The longitudinal fibres are outside these, and are continuous in front with those of the gullet, and they end in the tissue, which connects the dense circular fibres of the sphincter together. The large cells of the inner coat of the stomach are not found on the basement membrane which covers the thick sphincter, and they cease suddenly a short distance in front of it.

This part of the stomach is evidently in very constant and somewhat violent movement, for thejuse of the dense mass of circular fibres is to compress and crush the food in its passage to the intestine; consequently, a cellular layer exists on the basement, which is suited to bear pressure. The cells of this part resemble to a great extent those of the gullet; they are flat, hexagonal, and pavementlike, but a great number of them have very decided tooth-like projections on their free surface (a, Fig. 4). These projections occur in numerous circular series, and they are sufficiently prominent to wound a delicate vegetable cell passing over them, and submitting to the pressure induced by the contraction of the circular fibres. It is evident that if the muscular contraction be great, and the cells of the leaf rather hard, these hexagonal tooth-bearers will suffer from much and perhaps destructive compression.

But a very interesting structure is superadded to this part of the digestive system in order to prevent such an accident to the delicate mucous membrane. There is a layer of very large flattish cells beneath the basement membrane and between it and the circular fibres. Each of these cells (6) contains much fluid within a very visible cell-bag, and there are the usual nuclei. They are not quite in opposition laterally, and they rest upon an expansion of the muscular fibres, some granular fluid and nuclei intervening (c). Their office is to act as cushions beneath the immediate seat of pressure, and where the circular fibres are the strongest, there they are best developed. This arrangement of fibres, cushion cells, basement membrane, and delicate tooth-like projections, is continued to the extreme end of the stomach. There the circular sphincter muscle exists, and the basement is folded more or less

ongitudinally, so as to admit of the calibre of the canal being extended and contracted to the utmost. The cell teeth are found here in angular series, and there is one circular row of large ones. Microscopic examination of the dense mass of circular fibres reveals that the fibres are separate, stout, and that some of them possess a structureless investing membrane (d). The longitudinal muscles of the stomach, which are extremely long and close together, end by forming one or even three processes, which are united to the circular fibres, and the corresponding fibres of the intestines take their origin in this sphincter. Many nerves and air-tubes supply this part, which ends in an intestine of moderate length, and which time will not permit me to consider.

These structures are all developed in exact relation with the gormandising habits and the nature of the food of the cabbage-eating larvæ. The pieces of raw vegetable consist of cells with tolerably stout walls, and these have to be broken into before any nutritious matter can be let out to be digested, and the growth of the insect is so rapid that the quantity of food swallowed and passed along the stomach is very great.

This active stomach has periods of rest during the skin-shedding, when the cells of its mucous coat are cast off and replaced by new ones. The day comes at last when the caterpillar loses its love for cabbage and is to get no more, and then, ere it hangs pendent before the alterations in the size of the segments commence, changes may be noticed to have begun in the anatomy just described, changes which might take place from disuse. The stomach is, comparatively speaking, empty of food, the club-shaped cells are smaller and less round, and the globular cells are broken up. The muscular fibres appear thinner, wider apart, and more transparent. Immediately after the agglutination of the outside of the pupa occurs, sensible changes proceed in the digestive canal, and very rapidly. By the fifth day the whole canal has become shorter, the gullet has become thread-like and longer than in the caterpillar. The stomach is not half the length or one-third of the breadth of its former condition, and the intestine is longer than before. A general atrophy of all the layers of muscular fibre exists, and the dense muscular sphincter of the stomach with its peculiar fibres has been absorbed and replaced by simple, separate, and delicate circular muscles. The longitudinal fibres are wide apart, and very transparent. The longitudinal folds of the gullet have disappeared with the mucous crypts, and the basement membrane is covered with a granular fluid, in which the remains of the old hexagonal cells float. A mass of broken-down, club-shaped globular cells occupies the small stomach, and a totally different arrangement covers the basement. Cells packed closely together here and there, and separated by lines of granules, indicate that a new kind of mucous coat is being developed. These cells assume the hexagonal shape, are moderately tall, and contain a few granules, and they extend over the place of the toothed cells at the sphincter, and join the cells of the intestine (Fig 5). The toothed cells have disappeared, and the cushion cells of the region of the sphincter also. All these structures are remarkably delicate and difficult to manipulate, and it may be remembered that they are not performing any function whatever.

The

When the imago escapes from its hard pupa case, and when it has completed its metamorphoses, the digestive canal presents further modifications, which are brought about, however, during the imprisonment. The gullet is longer, and has a sac-like crop projecting from it; the stomach is narrower, and the intestine is longer. All the muscular fibres are extremely delicate, and there are no new arrangements of them. The basement membrane of the gullet is developed on one side into a bag-shaped tissue, and the whole of it is covered by extremely delicate cells, most of which have a long hair-like process sticking up from them, which was foreshadowed by the tooth-like projection of the larva state. stomach cells have increased in height, and contain granules, but they resemble those of the pupa until the food is taken; then the cells increase in size, and many are set free in a globular form, and there is not a want of likeness between some of them and those of the larva (Fig. 6). This long gullet, crop, and tubular stomach, so flaccid from want of strong muscles, is admirably adapted for the peculiar food of the perfect insect. The sugary fluids of flowers require no crushing and rasping, and not much digestion-so the hairs of the gullet-cells assist in the passage of the syrup down the canal, and the gentle pressure of the delicate muscles of the stomach suffices for its purpose.

To say the least, these are wonderful changes in the same anatomical elements, and they indicate that metamorphosis in

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