EXPERIMENTAL- STUDY OF THE OYSTER GILL 2§ 



cover glass in a microaqiiariuin. The temperature of the water in the microa- 

 quarinm was regulated and kept constant within one-half of 1°. It has been found 

 that with the decrease in temperature below 15° C. the ciliary motion becomes slow 

 and irregular and ceases entirely at 5°. The experiments were repeated many times 

 with the same results. Different residts, however, were obtained when observations 

 were made on large pieces of the gill. Portions of the gill lamellae approximately 6 

 square centimeters in area were kept in a Stender dish of about 15 centimeters capacity 

 which was placed on a little platform built on the bottom of a finger bowl. The 

 space between the walls was filled with water and the temperature was kept constant. 

 The experiments were made in September, 1926, and February, 1927. The micro- 

 scopic examination made with a water immersion lens on the large pieces of gill 

 showed that when the temperature drops to 5° C there is a considerable slowing 

 down of the ciliary activity and the beating continues without a definite rhythm. 

 Due to the lack of coordination and irregularity of the ciliary niotion, no current is 

 produced. The activity of some of the cilia continues even at — 2° C, when almost all 

 the water in the dish except a narrow space just around the gill is frozen. A complete 

 cessation of ciliary activity occurs only when the water freezes entirely. The process: 

 is reversible, and as soon as the ice melts the cilia begin to beat again. It has beefl' 

 noted that at low temperatures some of the cilia cease beating sooner than others; 

 it is impossible, therefore, to speak of a definite critical temperature at which ciliary; 

 activity stops. In some of the filaments the motion stops as soon as the temperature 

 drops to 5°; in others it goes on until all the water is frozen. There is also a distinct 

 difference in the behavior of different kinds of cilia; frequently the lateral cilia come 

 to rest first while the frontal cilia continue to beat. 



The discrepancy observed in the experiments with small and large pieces of. 

 gills shoidd be attributed to the different conditions of the tissues and probably to 

 the lack of blood in the small pieces. Gray (1926) has shown that in the Mytilus 

 gills the cells of the lateral epithelium contain a supply of available energy sufficient' 

 to maintain their activity in sea water for a limited period of time. If the gills are 

 thoroughly washed with the sea water the lateral cilia come to rest in about 15 minutes. 

 In a well-fed mussel the period of activity may be considerably longer. The frontal 

 ciUa, however, remain active for a very long period. .ftin no .U oiui 



Several experiments were performed in February, 1927, with the view to deter- 

 mining whether the efficiency of the frontal cilia is affected by low temperature 

 in the same manner as that of the lateral cells. The oysters were taken from the 

 harbor when the temperature of the water was 0.8° C; after removing the left valves 

 and mantles the oysters, with the gills exposed, were placed in a tray filled with sea 

 water, the temperature of which was raised gradually. A few drops of carmine sus-* 

 pension, having the same temperature as that of the siirroimding water, were dropped 

 on the surface of each gill, and the temperature at which the carmine particles began 

 to move was recorded. The following is the record of one of the experiments (Feb- 

 ruary 3, 1927). At 11.45 a. m. eight oysters were taken from the harbor, opened, and 

 placed in water of 0.5° C. 



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