The larvae known as caddis-worms are aquatic. The mature females lay their eggs in the water, and the newly-hatched larvae provide themselves with cases made of various particles such as grains of sand, pieces of wood or leaves stuck together with silk secreted from the salivary glands of the insect.
Between ectoderm and endoderm is a supporting layer of structureless gelatinous substance termed mesogloea, secreted by the cell-layers of the body-wall; the mesogloea may be a very thin layer, or may reach a fair thickness, and then sometimes contains skeletal elements formed by cells which have migrated into it from the ectoderm.
Humming-birds and honeysuckers are agents of pollination in certain tropical plants; they visit the generally large and brightly-coloured flowers either for the honey which is secreted in considerable quantity or for the insects which have been attracted by the honey (fig.
There is reason to suppose that, when a wound is inflicted by the central stylet, it is envenomed by the fluid secreted in the posterior proboscidian region being at the same time expelled.
For example, the trypsin of the pancreas (see Nutrition) digests albuminous bodies in neutral or alcoholic solution, and if the whole of that which is secreted in the pancreas for the digestion of meat in the intestine were absorbed unchanged into the circulation, it would digest the body itself and quickly cause death.
In Cephalodiscus the coenoecium is more massive, and may contain a continuous irregular cavity in which the zooids live (Demiothecia), or may be secreted in such a way that each zooid has its own independent tube (Idiothecia, Orthoecus).
In Sambucus and Viburnum the small white flowers are massed in heads; honey is secreted at the base of the styles and, the tube of the flower being very short, is exposed to the visits of flies and insects with short probosces.
The curious little Pselaphidae, with three-segmented tarsi, elongate palpi, and shortened abdomen; the latter are usually found in ants' nests, where they are tended by the ants, which take a sweet fluid secreted among little tufts of hair on the beetles' bodies; these beetles, which are carried about by the ants, sometimes devour their larvae.
So like a choice casket is it secreted in him, that I have known some whalemen who peremptorily deny that the Sperm Whale has any other brain than that palpable semblance of one formed by the cubic-yards of his sperm magazine.
CORAL, the hard skeletons of various marine organisms. It is chiefly carbonate of lime, and is secreted from sea-water and deposited in the tissues of Anthozoan polyps, the principal source of the coral-reefs of the world (see Anthozoa), of Hydroids (see Hydromedusae), less important in modern reef-building, but extremely abundant in Palaeozoic times, and of certain Algae.