EXPERIMENTAL STXTDY OF THE OYSTER GILL 



19 



cessation of the ciliary motion on a given area of the gill. Readings obtained with 

 Gray's method were so inconsistent that the method was discarded as unsuitable for 

 the oyster gill. The temperature optimum for Mytilus gills is somewhat higher than 

 that of the oyster. Gray's figures show that the highest activity of the Mytilus cilia 

 takes place at a temperature between 27° and 38°, while the maximum activity of the 

 oyster occurs between 25° and 30°. 



A comparison of the results of Gray's work on Mytilus and the data obtained 

 during the present investigation discloses the interesting fact that the curves describ- 

 ing the effect of temperature on the rate of flow of water and on the mechanical work 

 produced by the oyster gills are different from the curve showing the effect of tempera- 

 ture on the relative speed of Mytilus cilia. (Fig. 6.) As has been shown in another 



ER{^ 

 ^tC. 



14 

 13 

 12 

 II 

 10 



9 



8 



7 



6 



5 



4 



3 



2 



I 



10 



15 



30 



35 



40 



20 25 

 TtMRLRATURt' C. 



Fig. 6.— Effect of temperature on the relative speed ot ciliary activity of Mytilus (Gray's data) and on the rate 

 of flow of water and rate of doing work by the oyster. The vertical scale for the rate of doing work is shown on 

 the right side 



paper (GaltsoflF, 1928), the rate of flow of water is not a true expression of the mechan- 

 ical activity of the gUls. With the decrease in temperature the viscosity of water 

 increases, and therefore the resistance to fluid motion increases also; consequently 

 more energy is required to propel cold water at a given velocity. The work expended 

 in producing a steady current through the horizontal glass tube can be computed 

 from the following formula (Galtsoff, 1928): 



F=27rZMS' 



(5) 



where Tr=rate of doing work in ergs per second, Z = length of the tube in centimeters, 

 /i = viscosity of water in poises, and 5 = speed at the axis of tube in centimeters per 

 second. 



