The science of life : fully illustrated in tone and line and including many diagrams

FURTHER PATTERNS OF INDIVIDUALIZED ANIMAL LIFE

source of delight to those fortunate enough to possess a microscope. “If, retaining sense and sight, we could shrink into living atoms and plunge under the water, of what a world of wonders should we then form part ! We should find this fairy kingdom peopled with the strangest creatures : creatures that swim with their hair, and have ruby eyes blazing deep in their necks, with telescopic limbs that now are withdrawn wholly within their bodies and now stretched out to many times their own length. Here are some riding at anchor, moored by delicate threads spun out from their toes, and there are others flashing by in glass armour, bristling with sharp spikes or ornamented with bosses and flowing curves ; while, fastened to a green stem, is an animal convolvulus that by some invisible power draws a never-ceasing stream of victims into its gaping cup, and tears them to death with hooked jaws deep down within its body.” (Hudson .and Gosse in their classical monograph of The Rotifera, 1886.) The rotifers are neither useful nor harmful to man; their interest lies almost entirely in this microscopic esthetic appeal.

The Polyzoa, including the socalled sea-mats, are equatic and most of them are marine. At first sight they look like the hydroid polyps to be presently described, for they are small animals living in colonies, and each individual has a circlet of tentacles surrounding its mouth; nevertheless, they are very much more elaborately organized than hydroids, although most people take them for plants. Their colonies are supported by horny, slimy, or gelatinous skeletons, generally intricate and often beautiful when seen through the microscope. There are an enormous number of different species. Polyzoa are very common on the seashore, forming encrustations on seaweeds, rocks, crabs and the like; the fresh-water forms, by clogging the pipes and filters of water-works, may become a serious nuisance.

The Brachiopods or lamp-shells are marine

animals having a shell that looks at first sight like the shell of a bivalve mollusc. A lamp-shell leads the life of an oyster or a mussel, lying at the bottom of the sea, collecting suspended particles of food by means of a ciliated sieve that works like the gills of a clam or the pharynx of a sea-squirt, snapping together the two shields if any danger threatens. Nevertheless, their organization is very different from that of bivalves. The two halves of the shell, for example, correspond to the back and front of the creature and not to its right and left as they do in bivalves. And the food-filter is made in a

Fig. 95. Superficially like a clam, but very different in its inner organization—Terebratula, a kind of lamp-shell (Brachiopod) from the deep water of the Faroe Channel.

peculiar and characteristic way. At one time they were classified with the molluscs, but now they are either put in a phylum by themselves, or with the polyzoa in the phylum Molluscoidea. At the present day there are about a hundred species of brachiopods living in the sea at various depths, but they are only the survivors of a group that flourished and attained a rich variety of forms in the Paleozoic era, and has declined steadily in numbers ever since. Slowly, for some reason, as the world aged the oyster and the scallop and the mussel took their place. But one genus, Lingula, living in the mud of warm seas, has continued the even tenor of its existence from a nearly incredible antiquity. It is the senior genus of the world of life.

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