The jellyfish is carnivorous, feeding on small organisms such as crustaceans and even fishes. The tentacles are invested with stinging-cells, as are also the frills about the mouth, when such occur. With these stinging-cells, which are in some species so powerful as to have been compared with an electric battery, the jellyfish benumbs its prey. The stinging properties are due to nettle-like threads contained in poison-cells. When these penetrate the flesh they produce a pain similar to that of an electric shock. The food is taken into the manubrium by the square mouth at its free end, and is there digested. It is then sent as nutritive fluid through the canal system of the body, and ejected through small pores in the canal which surrounds the margin of the umbrella. There are two sexes. The gonads of the female contain eggs; those of the male, sperms. The contents of the gonads drop into the central cavity and pass out through the mouth. The fertilized ovum is called a /planula/, and is a transparent sphere covered with cilia, by means of which it swims about for a time. At length it attaches itself to some object, and becomes in some species a branching colony (hydroid), in other species a /strobila/. The latter, as it grows, is constricted at intervals, and at maturity resembles a pile of inverted saucers with lobed edges. Each of [pg136] these saucers is finally detached, and when liberated is called an /ephyrula/, and becomes a jellyfish. Thus its cycle of life is complete. There are some species which, having no hydroid or strobila state, mature without alternation of generation (/metagenesis/). The term of life of the jellyfish does not exceed one year. Even the giant /Cyanea/ attains its immense growth in six months. It starts in the spring as an ephyrula, not more than one half of an inch in diameter, and when it dies in the autumn is often six to eight feet in diameter. The bodies of jellyfishes are ninety-nine per cent. water, and the dead ones thrown upon the beaches by the autumn storms rapidly disappear, leaving no traces behind. The powerful stinging-cells with which the large medusæ are armed make them formidable enemies, and it is probable that some deaths by drowning are caused by swimmers encountering them and becoming paralyzed by them. ORDER =STAUROMEDUSÆ= ("/Cross-medusæ/") GENUS ^Lucernaria^