legs. On the seaweeds, as well as in the tide-pool, may be found beautiful hydroids, and on [pg009] them the curious little sea-spiders (Pycnogonidæ), animals which seem to be all legs.

Mollusks, and other classes as well, differ in different latitudes. On the rocks of the Northern shores Littorina and Purpura shells are very abundant, the latter in various colors and beautifully striped. Limpets are also plentiful, but are not as conspicuous, since they have flat, disk-shaped shells. When their capture is attempted, they must be taken unawares and pushed quickly aside, else they take such a firm hold of the rock that it is difficult to dislodge them. Near low-water mark under ledges will perhaps be found chitons, which are easily recognized by their oval, jointed shells. On the California coast in like localities will be found the beautiful Haliotis, Acmæa, and chitons. Every stone that is lifted will disclose numbers of little amphipods (Gammarus), which will scuttle away on their sides to other shelter; worms will suddenly disappear into the mud, and perhaps a crab, here and there, having no alternative, will make a stand and fight for his liberty. Flat against the stone and not easily perceived may be a chiton, a planarian worm, or a nudibranch. And just below the water's edge are sea-urchins and starfishes, which grow in numbers as the eye becomes accustomed to the search.

The rock pools are natural aquaria, more interesting by far than any prepared by man. The possibilities of these little sea-gardens are beyond enumeration. The longer one studies them the more one finds. In them all classes of seaweeds and marine invertebrates may be found and their habits watched. The great beauty of these pools gives them an esthetic charm apart from the scientific interest they excite. Perhaps one may find here a sponge, and removing it to a shallow vessel of sea-water can watch the currents of water it creates. Several sponges of the same species placed in contact will at the end of two days be closely united. If the sponges are of different species they will not coalesce.

In the clefts and crannies of the rocks are various fine seaweeds, often of the red varieties, sea-anemones, hydroids, polyzoans, crustaceans, mollusks, and ascidians. Crabs will be snugly [pg010] ensconced under projecting surfaces. Most species are more plentiful at the lowest-water mark, and many are found only at this point and below.

SANDY SHORES

On sandy shores the greater part of the inhabitants live under the surface. Many give evidence of their presence by the open mouths of their burrows, and some distinctly point out these places by piles of sand or mud in coils at the opening. Some tubicolous worms have their tubes projecting above the surface. The tubes of Diopatra are hung with bits of shells, seaweeds, and other foreign matter. Some mollusks announce themselves by spurting jets of water or sending bubbles of air from the sand. The majority of the underground species, however, give no sign of their presence on the surface, and must be found by digging. Many of them go deep into the sand, and in searching for worms the digger must be quick- and expert, or he will lose entirely or cut in two many of the most beautiful ones, which retreat quickly and to the extremity of their holes at the least alarm. One can be a rambler on the sandy beach for a long time without being aware of the many beautiful objects which inhabit the subsurface of the sand. The curious crab Hippa will disappear so quickly into the sand that one is hardly sure he has really seen it. The vast number of worms will surprise any one who searches for them by their variety, their beautiful color, and their interesting shapes. Here again a glass is requisite to appreciate the delicacy and beauty of their locomotive organs, their branchiæ, and so on. The most common of the gasteropod mollusks on sandy shores are Nassa obsoleta, Nassa trivittata, and Polynices (Lunatia) heros. The last are detected by the little mounds of sand which they push before them as they plow their way just below the surface. On more southern beaches, Fulgur, Strombus, and Pyrula are the common varieties. Olivella, Oliva, and Donax, also inhabitants of sandy beaches, will quickly disappear when uncovered by the waves, being rapid burrowers. Most of the many dead shells on the beach will be found to be pierced with a round hole, which is [pg011] drilled by the file-like tongue, or lingual ribbon, of Polynices, Urosalpinx, or Nassa, which thus reach the animal within and suck out its substance. Another similar species is Polynices (Neverita) duplicata, which extends to the Gulf of Mexico, while P. heros is not commonly found below Hatteras. Crustaceans are abundant on the sandy beach over its whole breadth. Some of the sand-crabs live above tide-mark. Among these is the fleet-footed Ocypoda, which is interesting to watch. Often they go in numbers to the water's edge and throw up mounds, behind which they crouch like cats, watching for whatever prey the tide may bring up. When unable to outrun a pursuer they rush into the surf and remain there until the danger is past. The wet sand is often thickly perforated with the burrows of the sandhoppers (Orchestia). These often rise about the feet as do grasshoppers in the fields.

PLATE I.
Egg-capsules of Purpura lapillus.	Egg-case of Polynices heros.
Egg-capsules of Buccinum undatum.	Egg-case of the skate.
Fulgur canaliculata (whelk) and egg-cases.

Hippa talpoida is a remarkable crab, somewhat resembling an egg. It is not likely to be seen unless searched for by digging at the water's edge. It burrows so rapidly that one must be quick to catch it after it is exposed by the shovel. In some places the tests of "sand-dollars" are common. The living animal may be found buried just below the surface at extreme low-water mark.

The sea-wrack drifted in lines along the shore will repay careful examination, for here will be found many things belonging to other shores and deep water. It is often alive with sandhoppers, which hop away while one searches for less common things. Often the most delicate seaweeds, numerous small shells, worms, polyzoans, etc., will be found there.

The surface of the sand-beach is strewn with remains of many species, usually beach-worn, but interesting nevertheless as examples of species one would like to find in better condition, but good specimens of which elude ordinary search or are unobtainable except by dredging.

Egg-cases form another class of objects which are often gathered with no idea of their identity. Of these the most common are the long strings of saucer-like capsules which contain the eggs of the mollusk Fulgur, those having square edges being [pg012] the egg-cases of F. carica, and those having sharp edges those of