20 BULLETIN OF THE BUREAU OF FISHERIES 



' ' ' '■ Analyzing the curves of the effect of temperature on the rate of doing work and on 

 the rate of flow of water, one finds that neither curve can be described by the 

 Arrheniiis equation, which was found apphcable to many instances of the effect of 

 temperature on biological reactions. Crozier (1924) has found, however, that the 

 effect of temperature on the relative speed of the Mytilus cilia follows this equation. 

 The discrepancy undoubtedly is due to the fact that the rate of flow of water is con- 

 trolled not only by the frequency of the ciliary beats (which may depend on a definite 

 chemical reaction) but also is governed by several other factors, such as rhythm and 

 coordination of the ciliary motion along the whole surface of the gill. The production 

 of a current by the gills is a very complex phenomenon in which several reactions of 

 the orgatiism are involved. 



Although the rate of flow of water does not give us a true measure of the activity 

 of the gills, it supplies information regarding the effect of temperature on the feeding 

 of the oyster; the latter is obviously dependent on the volimie of water that the 

 oyster is capable of passing through the gills at various temperatures. 



It has been shown above that the rate of flow of water produced by oysters of the 

 same age and taken from one locality is subject to wide individual variation. For 

 instance, the highest figure of discharge of water measured at 25° was 3.9 liters per 

 hour, while another oyster at the same temperature produced a flow of water at the 

 rate of only 0.9 liter per hour. The results of the experiments discussed above are 

 consistent in the respect that in all of them there was a decrease or increase in the 

 rate of flow depending on the direction of the changes in the temperature. It is inter- 

 estiing to compare the data obtained in these experiments with the estimates computed 

 by other investigators and based on the counts of planktonic forms foimd in the 

 stomachs of the oysters. The comparison is difficult, however, because of the failure of 

 the investigators to give temperature readings at the time of their experiments. 

 Assimaing that the experiments were made in summer, it is very likely that the tem- 

 perature at which the observations were made was somewhere between 18° and 24° C. 

 As is shown in Figure 4, at this temperature interval the rate of flow of water in the 

 majority of oysters varies between 1..5 and 2.5 liters per hour. Grave (1905) states 

 that the oyster filters 0.167 liter per hour. Moore (1913) estimates that an oyster 

 takes in water at the rate of 40 quarts (38 liters) a day but fails to state whether the 

 .filtering was going on continuously for a 24-hour period. Wells (1916) states that 

 "at feeding temperatures large volimies of water, from 25 to 50 gallons a day, pass 

 through the oyster gills." In another paper (Wells, 1926) he says that " the quantity 

 of water filtered through an oyster gfll at moderate temperatures averaged greater 

 than 2 gallons per hoiu-." As has been shown in the present paper, "feeding temper- 

 ature" covers quite a wide range — from 7° to 40° C. Unfortunately Wells does not 

 state how he arrived at these figures. It is doubtful that there are oysters that are 

 able to take in water at the rate of 7.5 liters (2 gallons) per hour, and Wells's figures 

 should be regarded as guesses not supported by any experimental evidence. 



Nelson's (1921) estimate of the rate of flow of water through the oyster is 6 

 quarts (5.7 liters) per hour. Allen (1914), for a fresh-water mussel, gives a rate of 

 flow of 1.4 Uters per hour. The filtering of water by the sea mussel has been studied 

 iu Conway Laboratory (England). According to a statement found in the Guide to 



