Page:Popular Science Monthly Volume 78.djvu/607

Rh sea-water pump (Fig. 16), up to the reservoir. The air pump (Fig. 16, Q), driven by an electric motor, forces air, which may be diluted by the attachment (P), or compressed to five atmospheres (R), into five tanks holding 455 liters (T), from which, by means of a reducing valve (U), it is allowed to escape under a pressure of from 1.1 to 1.2 of an atmosphere and is then distributed (V) to the aquaria. In the case of delicate animals, or eggs, solitary or in masses, the air must issue from the terminal plug in very fine bubbles. The outflow is through a plug of bamboo, or merely a piece of finely perforated rubber, while for the larger basins, charcoal or pumice is used. A natural plankton and bottom fauna develops, which is of interest

 A, reservoir; B, outlet pipe; C, ebonite cock; D, basin; E, F, removable outlet pipe and plug; G, outlet pipe; H, filter basin; K, cistern; L, riser pipe; M, pump; N, inlet pipe. Aeration Apparatus: O, inlet filter; P, attachment for air dilution; Q, air pump; R, attachment for air compression; S, manometer; T, air reservoir; U, reducing valve; V, conducting pipes; W, outlet; X, flexible connection; Y, glass tube; Z, excurrent perforated plugs.

as material for investigation and important as food for animals under experimentation. Such forms appear as small hydromedusæ, ctenophores, worms, ascidians and numerous copepods. Much additional food is required and for this chopped fish, or other meat, is used, but given in small quantities to avoid spoiling the water. Tunicates and mollusks like Nassa and Mytilus, placed in the larger aquaria, quickly remove the food débris. Protection from the sun is necessary to prevent an excess of green algae from obscuring the subjects of experimentation. In the small covered jars the proper