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, { PLATYHELMINTHES, { _A._ TURBELLARIA or PLANARIANS. BUT WITHOUT { or FLAT-WORMS. { _B._ CESTODA or TAPE-WORMS. BODY-CAVITY. { { _C._ TREMATODA or FLUKE-WORMS. =Grade IV.= { NEMERTINES. WITH MESODERM { NEMATODA or THREAD-WORMS. AND { HIRUDINIA BODY-CAVITY. { or LEECHES. { _A._ ARCHIANNELIDS. { { { CHÆTOPODA. { _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