ent 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 
brought nearer the opening into the stomach, and then it is forced 
_ into that organ by the progressive contractions of the circular 
fibres. The piece of leaf is lubricated by the granular mucus of 
the crypts, and is squeezed by the contraction of the circular 
fibres. 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 activé 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 mem- 
brane, 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 diges- 
tion, 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 remark- 
able, 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 some- 
what violent movement, for thejuse of thedensemassof circular fibres 
is to compressand crush the food inits passageto the intestine ; con- 
sequently, a cellular layer exists on the basement, which is suited 
to bear pressure. The cells of this part resemble to a great ex- 
tent those of the gullet ; theyare flat, hexagonal, and pavement- 
like, but a great number of them have very decided tooth-like pro- 
jections 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 deli- 
cate 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 (4) contains much fluid within 
a very visible cell-bag, and thereare the usual nuclei. They are 
notquitein 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 
5 sphincter muscle exists, and the basement is folded more or less 
"attached to a ring behind the mouth, and around the commence- | 
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 re- 
veals that the fibres are separate, stout, and that some of them 
possess a structureless investing membrane (¢). The longitudinal 
muscles of the stomach, which are extremely long and close to- 
gether, 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 gor- 
mandising habits and the nature of the food of the cabbage-eating 
larvae. The pieces of raw vegetable consist of cells with tolerably 
stout walls, and these have to be broken into before any nutri- 
tious 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 haye 
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 dis- 
appeared 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 tootlied 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 deli- 
cate and difficult to manipulate, and it may be remembered that 
they are not performing any function whatever. 
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 mus- 
cular fibres are extremely delicate, and there are no new arrange- 
ments 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 fore- 
shadowed by the tooth-like projection of the larva state. The 
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- 
a 
