Infusorial animal life, as vorticellæ, stentors, rotifers, and various polyzoa, cling, as also do hydra, in colonies to vallisneria, duck-weed, frogbit, or small branches dipping down under water; and if some of the water-weed is brought home the little creatures will live and thrive for several weeks. No waters, however, are so full of minute animal life as the sphagnum bog. A number of species of diatoms, as well as protozoids and the smaller molluscs, will be found in all peat bogs. It is remarkable, too, that the same species, everywhere, are associated with this kind of moss. Lord Sidney Godolphin Osborn supplied his friends with moss growing in a damp part of the garden walk of his rectory; this always furnished the same species of rotifers. These proved to be most interesting objects to my friends, and in an early communication I described them as _indestructible_, since they will bear any amount of desiccation; nevertheless, they were revived when a drop of water was introduced into the glass-cell. [Illustration: Fig. 266.--Collecting Stick, Bottle, Hook, and Net.] The Thames mud always furnishes a number of beautiful forms of triceratum. Lower down the river, as brackish water is reached, greater varieties of diatoms appear. But to secure them the collector must be provided with a collecting stick. A convenient form is furnished by Messrs. Baker (Fig. 266). This consists of an ordinary walking-stick, together with a lengthening rod, a cutting hook to clear away weeds, ringed bottles with screw tops, and a net with a glass tube attached. Their uses are too obvious to need further description. The siliceous skeletons of diatoms are met with in the fossil state. Among the first discovered of the infusorial strata were the polishing slates of Bilin and Tripoli, the berg-mehl or mountain meal, the entire mass of which is composed of the siliceous skeletons of different species of diatoms. Richmond, Virginia, is rich in the same organisms, while the great mass of our chalk cliffs are composed of foraminiferous shells, xanthidiæ, &c. One remarkable fact in connection with fossil infusoria is that most of the forms are still found in the recent state. The beautiful engine-turned discs, _Coscinodisci_, so abundant in the Richmond earth, may be met with in our own seas, and in great profusion in the deposits of guano on the African and American coasts, and in the stomachs of the oyster, scallop, and other salt-water molluscous animals common to our shores. A great number of infusorial earths may be mounted as dry objects, while others require careful washing and digesting in appropriate media. The finer portions of the sediments will be found to contain the better and more perfect siliceous shells. Preparing and Mounting Apparatus. [Illustration: Fig. 267.--Mounting Apparatus.