1922] Blum: On the Effect of Low Salinity on Teredo Navalis 355 



then slopes abruptly down to 4 parts per 1000. This rapid decrease in 

 the number of siphons extended in salinities below 6 parts per 1000 

 indicates that, below this point, the vital functions are abruptly 

 interfered with in a large number of individuals. 



1 2 3 4 5 ti 7 S 9 10 11 12 13 14 15 



Salinity in parts per 1000. 



Fig. 2. Graph representing activity of Teredo navalis in water of 

 various salinities. 



The reduction of activity in these lower salinities is also indicated 

 by the cessation of boring activity. The degree of this activity was 

 estimated from the amount of chips ejected which collected on the 

 bottom of the aquarium. In the salinity of 7 parts per 1000 and 



