for several days. For long-term observations 

 it is more practical to use a water v/heel made with 

 two plastic disks mounted on a horizontal glass 

 rod about )2-inch apart. The space between the 

 disks is divided by radial partitions into a series 

 of triangular compartments. The wheel is placed 

 under the overflow tubing of the small vessel 

 which receives water discharged by the oyster. 

 The compartments are arranged in such a way 

 that when they are full of water the wheel turns 

 slightly and the next empty compartment moves 

 into position under the pipe. The wheel is kept 

 half submerged in sea water to prevent spinning. 

 Under this condition tlie rotation proceeds in 

 smooth steps; when the wheel makes one com- 

 plete turn tlie little bar attached to its side touches 

 a string which moves tlie writing lever and makes 

 a vertical stroke on a slow moving drum of the 

 kymograph. The construction of the wheel (F) 

 and the arrangement of different parts of the 

 set in which it was used are shown in figure 170. 

 The wheel is calibrated by measuring the volume 

 of sea water needed to make it turn one complete 

 revolution. The test is repeated at least 10 times, 



and the average value is taken as the true capacity 

 of the wheel. Wheels of different dimensions 

 may be used. In my e.xperiments I used wheels 

 of about 50- and 100-ml. capacities; the readings 

 were accurate within ±2.5 percent. 



The setup shown in figure 170 is specifically 

 designed for studying the effects of various con- 

 taminants that may be added at a known rate to 

 the water supplied to tank E. Sea water from the 

 laboratory supply pipe C is delivered to three 

 5-gal. carboys from which it runs into two temper- 

 ing jars with electric heaters (group B) and 

 vessel C. The water then passes into mixing 

 chamber D to which the solution to be tested may 

 be added from the two flasks and N, which 

 contain known concentrations of chemicals or a 

 desired dilution of a culture of microorganisms. 

 Test solutions in flasks O and N may be added 

 directly to the gills (as shown in the diagram, 

 flask N) or may be delivered to the mixing cham- 

 ber D. If the solution is to go into the mi-xing 

 chamber the siphon from flasks N or O is turned 

 around 180° so that the tip of the delivery pipe is 

 at the right end of the mixing chamber D. This 



Figure 170. — Setup for automatic recording of the amount of water transported by the gills of the oyster. A — series of 

 5-gal. containers from which sea water is delivered to the tank with the oyster; B — two containers with electric heaters 

 and thermostatic control (not shown in the diagram); C — constant level jar from which water is delivered to mixing 

 chamber D; E — tank with oyster wrapped in apron; F — water w^heel; H — container in which the water wheel is 

 partially submerged; K — kymograph; L — writing lever activated by the turning of the water wheel; M — writing 

 lever recording shell movement; \ and O — flasks containing solutions or suspensions which may be added either to 

 the mixing chamber or directly to the gills of the oyster. 



TRANSPORT OF WATER BY THE GILLS AND RESPIRATION 

 733-S51 0—64 13 



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