431 



1908.] NATURAL SCIENCES OF PHILADELPHIA. 



Table VIII. 

 Experiment 200. 



Experiment 201. 



Experiment 202. 



plant and no snail, and one with water plant together with tw^o snails. 

 After ten days the water was analyzed. The following facts seem to be 

 illustrated by these experiments: (1) Calcium and chlorides in the 

 water do not seem to be affected by the excretions of the snail. (2) 

 In the jar that contained no snails yet contained Myriophyllum nearly 

 all the free ammonia was taken up by the water plant. This is a 

 phenomenon well known to botanists (Sachs, 75 ; Bessy, '92). 

 Vernon ('99) found that the presence of Ulva decreased the free 

 ammonia, but increased the albuminoid ammonia. 



