. Animal studies. 52 ANIMAL STUDIES preceding group (Fig. 24), but while the latter are generally very small, these forms are commonly from four to twelve inches in diameter, and some measure one to two meters (three to six feet) across the bell. They are also distin- guished by means of tentacles which extend from the cor- ners of the mouth sometimes to a distance of several feet, and together with the marginal tentacles are formidable weapons for capturing small crabs, fishes, and other ani- mals which serve as food. In turn these forms serve as the food' of many whales, por- poises, and num
. Animal studies. 52 ANIMAL STUDIES preceding group (Fig. 24), but while the latter are generally very small, these forms are commonly from four to twelve inches in diameter, and some measure one to two meters (three to six feet) across the bell. They are also distin- guished by means of tentacles which extend from the cor- ners of the mouth sometimes to a distance of several feet, and together with the marginal tentacles are formidable weapons for capturing small crabs, fishes, and other ani- mals which serve as food. In turn these forms serve as the food' of many whales, por- poises, and numerous fishes which hunt them down, though the amount of nourishment they contain is prob- ably relatively small owing to the fact that in their composition there is a large percent- age of water (99 per cent in some species). The lobed margin of the bell, the absence of a definite swimming organ or velum, and the character of several of the internal organs, distinguish the larger from the smaller jelly-fish ; but the greatest differ- ence, however, is in the method of development. 49. Development.—The eggs arise from the inner layer of the jelly-fish and drop into the gastric cavity, where each develops into a ciliated two-layered sac in some respects like that of a young sponge. Swimming away from the parent, they finally settle down, and attaching themselves (Fig. 25, a) assume the external form and habits of the sea-. Fig. 24.—A jelly-fish (Rhizos(oma), about one- fourth natural Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Jordan, David Starr, 1851-1931; Kellogg, Vernon L. [from old catalog].
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Keywords: ., bookauthorjordanda, bookcentury1900, bookdecade1900, bookyear1903
