1815.] Royal Institute. 227 
have ap analogous structure with crustaceous animals. ‘There was 
reason to believe that the plates placed under their skin were sub- 
servient to their respiration, as they are in the fresh water shrimps; 
which approach very nearly to the cloport. But the fact remained 
to be established, and an apparatus remained to be shown, either at 
their surface, or in their interior, proper for this function. 
M. Latreille, Correspondent, who has been lately named a 
member of the Class, has filled up this gap in zoology. He has 
shown on four of the plates in question a little yellow part, pierced 
with a hole, and containing within it small filaments, a part which 
he compares to those which, though differently placed in the spiders 
and scorpions, have, however, an analogous structure, and fulfil the 
same function. However, notwithstanding this partial resemblance, 
and notwithstanding the existence of a sort of spinning apparatus, 
which he has observed in the cloportee, and which is analogous to 
thar of the spiders, M. de Latreille still leaves the cloporte among 
the crustaceous animals, on account of the much more numerous 
relations which they have to that class, 
The insects have for a long time been divided into two categories, 
according to the structure of their mouth ; one set having jaws well 
developed, and capable of dividing solid food ; and another having 
only a kind of sucker, fit only to draw in liquids. There are some 
insects which at different periods of their life have each of these 
forms of mouth, and which become suckers in their perfect state; 
though they were bruisers or chewers in their state of ‘larvee. Such, 
for example, are the butterflies, which employ for nourishment a 
double trump, usually in a spiral form, which they unroll to intro- 
duce into the bottom of the corolla of flowers, and to suck up the 
nectar there contained. While the caterpillars, which are merely 
butterflies not yet developed, have mouths armed with strong nian= 
dibles, with which they cut the hardest leaves, _ It was believed that 
the caterpillar, on assuming the wings, the long feet, the beautiful 
antenne of the butterfly, assumed also its trump, and lost entirely 
its Jaws. , 
M. Savigny, Member of the Institute of Egypt, has proved by 
delicate and long continued researches that this is not entirely the 
case; but that Nature in this circumstance, as in many others, 
confines herself to diminish certain parts, and to increase others, 
and that she arrives at effects entirely opposite by this simple change 
of proportions. He has discovered at the bottom of the trump of 
butterflies two organs exceedingly small, but which represent the 
mandibles of the caterpillars. At the back of the support of this 
same trump he has found two very small threads, which appear to 
him analogous to the maxillary palpe; so that the two plates of 
which the trump is composed are, according to M. Savigny, the 
extremely elongated points of the maxilla, that is tq say, of the 
inferior pair of jaws. Finally, the great palpas known to all natu- 
ralists are the palpa of the inferior lip, The two small maxillary 
P 2 
