1922] Blum: On the Effect of Loir SaZmity on Teredo Navali 



36] 



thin coating of paraffin. These specimens were exposed simultaneously 

 with the untreated specimens in aquaria through which currents I> 

 and C were passing. All the specimens contained approximately the 

 same number of live teredos at the beginning of the run. After 

 seven days the specimens were changed to water of 15 parts per 1000 

 salinity. Table 5 gives the approximate number of individuals 

 surviving under the various conditions. 



TABLE 5 

 Survival op Teredo navalis in Running and Standing Fresh Water 



A > B > C. 



Table 5 shows that the survival was greater in standing water than 

 in running water, and greater in slowly running water than in swiftly 

 running water. Specimens having the cut surfaces protected by a 

 coating of paraffin, and therefore having less surface exposed for 

 diffusion of water, show a greater survival than untreated specimens. 

 The explanation of the dilution of the water in the burrow by a 

 process of diffusion through the wood accounts for the above results, 

 since the rate of diffusion would be expected to increase with the rate 

 of flow of the current. This would shorten the time necessary for 

 dilution of the water in the burrow, a condition which would be 

 followed by the death of the teredos. The speed of such a process 

 would also be decreased by reduction of the surface of the specimen 

 by covering the cut surfaces with paraffin. 



Table 3 shows that teredos lived longer in specimen blocks in 

 water of 2 parts per 1000 salinity than in zero salinity. This may be 

 due to the fact that diffusion takes place less rapidly between solutions 

 nearer the same concentration than between solutions having a greater 



