MARINE TOXINS AND VENOMOUS AND POISONOUS MARINE ANIMALS
275
phylum have nematocysts, of which there are many different kinds,
and individual animals may possess more than one kind of nematocyst. While all cnidaria are potentially dangerous, only a few have
nematocysts capable of penetrating the skin and poisoning humans.
The reader is referred to the fine works of Weill (1934), Hyman (1940)
and F. S. Russell (1953) for a more complete study of the nematocyst.
The cnidoblwts are small rounded or ovoid cells which are widely
distributed throughout the epidermis, except on the basal disc. Particularly abundant on the tentacles, they are used both as offensive and
FIU. 2. Diagrammatic sketch of an undischarged (left) and discharged (right) nematocyet
of a cnidarian. (Modified from Halstead, 1969.)
defensive weapons, as well as for aids in anchorage. The typical cnidoblast contains a basal nucleus, and a capsule, the nematocyst, containing
a long coiled tube or hollow thread. In Hydra the thread of penetrant
nematocysts (stenoteles) appears to be continuous with a " head " which
may contain the venom (Chapman, 1961). A short, bristle-like projection, the cnidocil, is embedded in a crater on the discharge end of the
cell (Fig. 2). I n the stenoteles of Hydra an operculum covers the
junction of the undischarged thread to the capsule. The thread
may vary in length from 50 p to 1 mm, while the nematocyst itself is
0 2
275
phylum have nematocysts, of which there are many different kinds,
and individual animals may possess more than one kind of nematocyst. While all cnidaria are potentially dangerous, only a few have
nematocysts capable of penetrating the skin and poisoning humans.
The reader is referred to the fine works of Weill (1934), Hyman (1940)
and F. S. Russell (1953) for a more complete study of the nematocyst.
The cnidoblwts are small rounded or ovoid cells which are widely
distributed throughout the epidermis, except on the basal disc. Particularly abundant on the tentacles, they are used both as offensive and
FIU. 2. Diagrammatic sketch of an undischarged (left) and discharged (right) nematocyet
of a cnidarian. (Modified from Halstead, 1969.)
defensive weapons, as well as for aids in anchorage. The typical cnidoblast contains a basal nucleus, and a capsule, the nematocyst, containing
a long coiled tube or hollow thread. In Hydra the thread of penetrant
nematocysts (stenoteles) appears to be continuous with a " head " which
may contain the venom (Chapman, 1961). A short, bristle-like projection, the cnidocil, is embedded in a crater on the discharge end of the
cell (Fig. 2). I n the stenoteles of Hydra an operculum covers the
junction of the undischarged thread to the capsule. The thread
may vary in length from 50 p to 1 mm, while the nematocyst itself is
0 2