The reader will have no difficulty in finding and identifying both Serpula and Spirorbis. Terebella is frequently washed up on a sandy shore. On the Lancashire coast one may feel sure of finding this and many other sand-dwelling animals, after an east wind. The east wind, driving back the water at low tide, kills these creatures with cold, and presently they are washed up dead or dying by the high tide. Pectinaria, another worm with a tube of sand-grains, in which, however, the body lies loosely within the tube, may also be found in thousands under the same circumstances.
TABLE SHOWING THE CLASSIFICATION OF VERMES OR WORMS
| Grade III. With Mesoderm, but without Body-Cavity. |  | PLATYHELMINTHES, or FLAT-WORMS. | | A. Turbellaria or Planarians. B. Cestoda or Tape-Worms. C.Trematoda or Fluke-Worms. | ||
| Grade III. With Mesoderm, and Body-Cavity. | | NEMERTINES. NEMATODA or THREAD-WORMS. HIRUDINIA or LEECHES. CHÆTOPODA. | | A. Archiannelids. B. Oligochæta. C. Polychæta. |  | (a) Tubieola. (b) Errantia. |
We must not forget to say something regarding the most commonly known member of the Vermes, the familiar earthworm. The worms are the first of the great group of animal life in which we find true land animals. There are terrestrial forms among the lowest worms, at least forms that live in earth that is damp; but the earthworm is in the strictest sense a terrestrial animal. Darwin showed that it not only dwells in the soil, but is in a sense the manufacturer of soil, since the fertility of the earth depends greatly upon the work of earthworms. They pass the soil through their bodies, digesting the organic particles they find in it, and thereby loosen the soil, reduce it to a state of fine division, and render it more fit to support the growth of plants. The "worm-casts" formed by the soil that the earthworm has passed through its body may not have been noticed by everybody. More obvious are the worm-casts in sand left by the sand-dwelling marine annelids. These everyone must have seen who has walked on a sandy shore at low tide.
The worms include many puzzling forms, which have not been alluded to here. Among these must not be forgotten the Rotifers, or wheel-bearing animals. These are of minute size, and when first discovered were therefore placed amongst the Infusoria. They are common in ponds.
CHAPTER VIII
ARTHROPODA, THE LOBSTERS, SPIDERS AND INSECTS
The above is a very descriptive name for a division which includes the Crabs and Lobsters and the Insects. Formerly they were included, along with the worms, under the name Annulosa, the Ringed Animals. They resemble these as possessing what is termed metameric symmetry, but they are distinguished from them as the Leggy Animals, a fact which is explained in the name, Arthropoda, joint-footed. Worms, as we have seen, have no true legs, but the Arthropods, theoretically, have a pair of legs to every ring. In some of the lower members of the group this is literally the case, the Centipedes, or hundred-footed animals, for example ([Fig. 13]). In higher forms the number of legs is greatly reduced; several successive rings may become merged with one another, losing, along with their independence, their legs. The true Insects, thus, have only three pairs of legs and the Spiders four.