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University of California Publications in Zoology [Vol.22 



Since at the end of twenty-two days a greater percentage of 

 teredos survived in the block not directly surrounded by water than 

 in the blocks exposed to water of either or 2 parts per 1000 salinity, 

 we may assume that in the latter case the water within the burrows 

 was diluted bv the fresh water from the outside. 



TABLE 4 



Survival of Teredo xavalis under Various Experimental Conditions 

 in Aquaria 



The process involved in this dilution of the water in the burrow 

 is probably one of diffusion through the wood of the pile and perhaps 

 between the pallets at the mouth of the burrow. It is also possible 

 that the organisms may continue to draw in small quantities of water 

 through their siphons, thus gradually diluting the water in the 

 burrow ; but this is not probable since it was found that teredos were 

 killed more rapidly by running fresh water than by standing fresh 

 water, which could hardly be explained by such a process. The above 

 observation is more readily explained on the basis of diffusion, as the 

 speed of this process would be increased by motion and change of 

 water. The following experiment shows some results obtained with 

 specimens in running water. 



A series of aquaria was arranged so that currents of water of three 

 different rates of flow could be passed through them. The rates of 

 flow were not accurately measured, but had the following relation : 

 A > B > C. A was the discharge of a three-quarter inch pipe, 

 C a flow of approximately five gallons per hour, and B intermediate 

 between these currents. Specimen blocks containing teredos were 

 exposed in these aquaria and in aquaria containing standing fresh 

 water. Two other specimens were prepared from ordinary specimen 

 blocks by covering the split surfaces and cut ends of the block with a 



