EXPERIMENTAL STUDY OF THE OYSTER GILL lAL 



the Fisheries Exhibit (Ministry of Agriculture and Fisheries, 1922), "a mussel can 

 pump at least 10 gallons of water through itself in 24 hours." Unfortunately I \fa,a 

 not able to find a description of the method employed in Conway Laboratory. 



The fact that the estimated figures of the rate of flow through the oyster vary 

 from 0.167 to 7.5 liters per hour is good evidence of the unreliability of the methods 

 employed by previous investigators. The estimation based on the count of the plank- 

 tonic froms found in the stomach and intestine can not be accurate. Everyone who 

 has had experience with quantitative plankton examination is familiar with the diffi- 

 culties encountered in obtaining reliable figures. Moreover, in the estimation of the 

 rate of flow by this method an assumption is made that all the microorganisms caught 

 by the gills are ingested by the oyster, which obviously is incorrect, as some of tliem 

 never reach the mouth of the oyster but are rejected into the pallial cavity, c, 



EXPERIMENTS WITH HIBERNATING OYSTERS 



In the experiments described above the oysters were exposed to sudden changes 

 in temperature. Observations have shoMTi that the period of 15 minutes during which 

 the organism was kept at a constant temperature was sufficiently long to produce an 

 effect on the ciliary motion. There arises a question, however, whether long-continued 

 exposure to low temperature would produce different reaction. Nelson (1926) thinks 

 "that with the slowly falling temperatures of autumn and early winter the oyster 

 becomes adapted to a lower range of temperature, so that although there is a sharp 

 decrease in ciliary movement below 5° activity does not entirely cease." For practical 

 purposes it is very important to know whether in winter the oysters respond to the 

 changes in temperature in the same manner as they do in summer. 



In order to study this problem, several dozens of oysters were left on the bottom 

 of Woods Hole Harbor, close to the United States Bureau of Fisheries pier, in Septem- 

 ber, 1926. The daily examination of temperature records taken at 8 a. m., noon, 

 and 4 p. m. shows that since December 5 the temperature of the water was below 

 40° F. (4.4° C), and during January and February it varied from 29.6° to 34° F. 

 (-1.4° C. to 1.1° C). On February 12, 1927, 36 oysters were taken from the harbor, 

 brought into the cold laboratory room (air temperature 3,5° C), and examined. 

 All the oysters appeared to be healthy and showed a new growth at the edges of the 

 shell. 



The purpose of the first experiment was to determine the exact temperature at 

 which the outgoing current begins to flow. The valves of the oysters were forced 

 apart and glass rods were thrust between them to prevent their closing. Then the 

 oysters were placed in cold sea water poured into a large, white enamel tray and the 

 temperature of the water was raised gradually from 1° to 9° C. The oysters were 

 kept from 30 minutes to one hour at a given constant temperature; observations 

 were made at 1° intervals, and the beginning of the flow of water from every oyster 

 was noticed by adding a few drops of carmine suspension. The temperature of the 

 suspension was always the same as that of the water in the tray. The results of this 

 experiment are presented in Table 5 and Figure 7. In order to facilitate a comparison 

 with the results of summer experiments, the latter data are shown in the right column 

 of the table. 



