34 BULLETIN OF THE BUREAU OF FISHERIES 



Table 6. — Effect of temperature on ciliary activity — Winter experiments 



' Next day. 



» Current very slow. 



As can be seen from an examination of Figure 8, the curve describing the effect 

 of temperature on the rate of flow of water produced by the gills of winter oysters is 

 quite different from what has been obtained in summer experiments. (Fig. 5.) In 

 both winter experiments (fig. 8) the curves show a very slight increase in the rate of 

 flow of water between 7° and 15°, while in summer the slope of the curve at this range 

 is quite steep. It has been noticed, also, that the current in winter oysters was less 

 regular and the fluctuations in the rate of flow at a given constant temperature were 

 wider than those observed at the same temperature duiing the summer. The expla- 

 nation of such a difference in the acti\-ity of the gills is found in the condition of the 

 gill epithelium. All the oysters examined in February had the gills covered with a 

 thick layer of mucus accumulated during the periods of inactivity. After being 

 kept in a tank at a temperature of 9° C, the oysters discharged large amounts of 

 mucus, which, being of less specific gravity than water, formed long strings of gelati- 

 nous substance suspended in water. It has been mentioned above that the accumu- 

 lation of the mucus clogs the water pores and interferes with the activity of the lateral 

 cilia. It is very probable that this factor is responsible to a great extent for a slow- 

 ness in response to the increase in temperature. 



TEMPERATURE AT WHICH THE CILIARY MOTION CEASES COMPLETELY 



It has been shown above that the production of a current that runs through 

 the gill chambers and which is caused by the beating of the lateral cilia is also depend- 

 ent on the rhythm and coordination of the ciliary motion along the whole surface 

 of the gill. The fact that at certain low temperatures no current is produced does 

 not necessarily mean that the cilia are at a standstill; the latter may beat irregularly 

 without maintaining a necessary head pressure inside the gill cavity, and although in 

 doing so they produce a certain amount of work, the efficiency of the gill is equaling 

 zero. It is interesting to determine, however, at what temperature a complete ces- 

 sation of the ciliary activity takes place. In 1926 (Galtsoff, 1926), a series of obser- 

 vations was made with very small pieces of gill epithelium that were kept under a 



