may without impropriety be noticed in this place. It consists of a reticulated web, of a white or yellow colour, the shreds of which, when examined by the microscope, are found to be constituted by small globules of animal matter. It is more or less compact in different insects, and even in the same insect according to its age, being loosest and most stringy in young individuals. It very nearly corresponds to the fat of the larger animals, but as chemical analysis has produced different results, its essential properties and uses cannot be considered always the same. Virtually, however, its uses may be regarded as twofold; first, to protect the various organs by forming a soft and elastic bed, which retains them in their place, and prevents them coming in too close contact with each other; secondly, to afford a certain degree of nutriment when the insect is not in a condition to receive food. In the latter case, it exactly corresponds to the store of fat found in hybernating mammalia, when they go into their winter quarters. It is particularly plentiful in the caterpillars of the Lepidoptera; as they go through their various metamorphoses it gradually becomes more scanty, till it almost entirely disappears in the mature fly. It is hence naturally inferred that it supplies the requisite nutriment during the pupal sleep, and is gradually absorbed to aid in the development of the newly formed parts. Next to caterpillars it is most abundant in Coleoptera, Orthoptera, Hemiptera, and Neuroptera; or, speaking generally, it is more plentiful in masticating than sucking insects. Some dis-
