Fig. 22 is a portion of the _Bugula_, with one of the curious “birds’-head” processes. These appendages have the most absurd likeness to a bird’s head, the beak opening and shutting with a smart snap (so smart, indeed, that the ear instinctively tries to catch the sound), and the head nodding backward and forward just as if the bird were pecking up its food. On Plate XII. Fig. 2, is a pretty zoophyte called _Gemellaria_, on account of the double or twin-like form of the cells; and Fig. 5 represents the _Antennularia_, so called on account of its resemblance to the antennæ of an insect. Fig. 22 is an example of a pretty zoophyte found parasitic on many sea-weeds, and known by the name of _Membranipora_. Two more specimens of zoophytes may be seen on Plate XI. as they appear under polarised light. Fig. 17 is the _Cellularia reptans_; and Fig. 20 is the _Bowerbankia_, one form of which occurs in fresh water. Among the worms we may refer to the beautiful little _Spirorbis_, whose tiny coiled spiral tube may be found attached to almost every sea-weed, and which, when placed in a trough of sea-water, protrudes its beautiful crown of plumes. In chalk or other soft rocks, again, the tubes of _Spio_, with its two long waving tentacles, may be found by hundreds. Then there are the centipede-like worms, which may be found under nearly every stone, and which belong to the great family of Nereids, provided with formidable jaws and stiff bristles of various forms. The Serpulæ are allied to the Spirorbis already mentioned. Parts of the so-called feet of one of these worms are shown in Fig. 36, where the spears or “pushing-poles” are seen gathered into bundles, as during life. One of them, on a larger scale, is shown in Fig. 32. The gorgeous hairs of Aphrodite have already been alluded to. In the sea the few species of Crustacea which fresh water offers to the observer in the shape of Cyclops and its allies become thousands, and their changes during development are numerous and puzzling. Who, for example, would suppose that the young stage of the Cyclops was indistinguishable in habits, and almost in form, from that of the barnacle which adheres to the rocks? Yet such is the case, and there are other metamorphoses even more startling. Fig. 25 is the larva of the common crab, once thought to be a separate species, and described as such under the name of _Zoæa_. The Mollusca proper will not afford us many objects, except in the form of their lingual ribbon, which may be extracted from the mouth, gently heated in _liquor potassæ_, and mounted in balsam after well washing, when the rows of teeth form splendid objects by polarised light. The palate of a whelk is shown in Plate XI. Fig. 19. Again, the gills of the mussel will afford a beautiful illustration of ciliary action. If a portion of the thin plates which lie along the edge of the shell be examined in a little of the liquor, the action may be splendidly seen, and watched for a long time (Fig. 39).