ADAPTATION OF OYSTER TO CHANGES IN SALINITY 
349 
occupying but a few hours. On the following day the medium was changed to a 
salinity of 29.46, and adaptation was almost immediate. 
During the preceding tests it appeared that adaptation to a considerable change 
in salinity is a very slow process, much of which occurs between the recordings on 
consecutive days. In order to obtain records of as many details as possible of the 
early stages of adaptation, the salinity was reduced to 14.60 parts per mille and 
during the following 12 hours records were taken which provided one hundred and 
twenty-five 5-minute periods. In figure 2 the results are given in detail for the 
Figure 2.— Adaptation to salinity of 14.60 p. p. m. following a change from salinity of 29.46 p. p. m. Series I. Values of .S and F 
refer to consecutive 5-minute periods. 17°-19° O. 
5 days during which this salinity was used. For the first 8 hours (Nov. 18), with 
minor exceptions, the valves remained relatively close together, and almost no water 
was pumped. During the following hour the shell consistently became wider open 
and the gills produced a slight flow of water. Recording was continued for several 
hours more, but the rate of flow increased very little. However, during the follow- 
ing 4 days the gills steadily recovered, though large variations both in rate of flow 
and in degree of openness of the valves may be noted. Even after 5 days of treat- 
ment recovery could not be called complete, for the values of F never reached the 
