EXPERIMENTAL BIOLOGY 597 



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 

 (i2), 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 (F) 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 inter- 



FiG. 15. Plan of the Sea-watek Aqcahia and the Aeration EguiPMBNT. 

 A, reservoir ; B, outlet pipe ; C, ebonite cock ; D, basin ; E, F, removable outlet pipe 

 and plug ; O, outlet pipe ; H, filter basin ; K, cistern ; L, riser pipe ; M, pump ; il, inlet 

 pipe. Aeration Apparatus : O, inlet filter ; P, attachment /or air dilution ; Q, air 

 pump ; R, attachment for air compression ; 8j manometer ; T, air reservoir ; V, re- 

 ducing valve ; V, conducting pipes ; ^y, outlet ; X, flexible connection ; Y, glan tube ; 

 Z, excurrent perforated plugs. 



est as material for investigation and important as food for ani- 

 mals under experimentation. Such forms appear as small hydro- 

 medusae, 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 Myiilus, placed in the larger 

 aquaria, quickly remove the food debris. Protection from the sun is 

 necessarj- to prevent an excess of green algae from obscuring the sub- 

 jects of experimentation. In the small covered jars the proper con- 



