. Cassell's natural history. Animals; Animal behavior. THE MEDUSA. simple or ramified, carry tlie digested food to the circular canal. No special organs of circulation exist, and respiration is effected by tlie membranes or skin of the disc. The fringe of tentacles around the disc may be very short and sparely developed, or these appendages may be many feet in length and very numerous. They are supplied with nematocysts, which are the stinging organs, and which are sufficiently annoying to some thin-skinned batliers. The nervous system may exist in relation to the eye-spots, and in a very rudi
. Cassell's natural history. Animals; Animal behavior. THE MEDUSA. simple or ramified, carry tlie digested food to the circular canal. No special organs of circulation exist, and respiration is effected by tlie membranes or skin of the disc. The fringe of tentacles around the disc may be very short and sparely developed, or these appendages may be many feet in length and very numerous. They are supplied with nematocysts, which are the stinging organs, and which are sufficiently annoying to some thin-skinned batliers. The nervous system may exist in relation to the eye-spots, and in a very rudimentary condition elsewhere. Small swimming Invei-tebrata are the food of the The methods of reproduction and development are very remarkable, and the dimensions of the full-grown disc are greatly in excess of those of the first stage of life. One great group of the Discophorw, including the com- mon Jelly-fish of the British .â seas, lay eggs in the autumn when they are swimming near to the coasts and estuaries. The parent dies, and the young escape from tlie eggs as little spherical bodies, covered with cilia. Each one attaches itself by its base to a rock or seaweed, and tentacles are formed at the other end, the body gradually becoming elongate. With growth some contractions occur around the young form, the first being just below the circle of tentacles. Tentacles soon appear on the edges of the con- traction nearest the base, and the edges of the other con- tractions simply become lobed. After a while these contractions become deep, ami the animal resembles a set of plates placed one over the other, the top and bottom ones having circlets of tentacles. At a certain period, when the whole is less than an inch in height, the entire structure breaks up; the top falls off and dies, and the bottom part remains fixed, whilst the rest separates into as many discs as there were contractions, and each swims off to Viecome a gigantic DLscophora. * This process is a good ex
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Keywords: ., bookcentury1800, bookdecade1890, booksubjecta, booksubjectanimals
