371 



in amount certainly much in excess of the production at that 

 time in Quiver Lake (.63) or the river (1.74). This large pro- 

 duction in this locality is then, it seems, to be attributed to im- 

 pounding and decaying vegetation combined with accession of 

 adventitious planktonts. 



The average monthly production (3.3) in this lake is on the 

 whole less than half that in the river (6.65) for the same period, 

 and it exceeds by over fourfold that in Quiver Lake (.74), through 

 which all its run-off passes to reach the river. Since the com- 

 parison of the two lakes is based on coincident collections, these 

 amounts may serve as a quantitative statement of the effect of 

 the environmental differences. As vegetation is much the same 

 in both lakes the difference in production must be attributed to 

 some other factor presenting a difference which may be corre- 

 lated with that in production. Such a factor is found in the 

 impounding action, which is at a maximum in Dogfish Lake 

 and is relatively much less in Quiver Lake at the point of our 

 collections, where creek and spring water of recent origin cause 

 a more rapid displacement of the contents of the lake and car- 

 ry away the products of decay of vegetation before the plank- 

 ton can reach the degree of development that it does in the 

 more stable waters of Dogfish Lake. 



The run-off from this lake in this year would thus tend to 

 enrich Quiver Lake, though not on an average of sufficient pro- 

 duction to enrich the river even if it could reach it without 

 mingling with that of Quiver Lake. However, owing to the fact 

 that this lake receives no tributary creek or spring water, and 

 except at high levels has no bottom-land current through it, we 

 must infer that its run-off is confined — excepting only at stages 

 of general overflow — almost wholly to stages of falling water. 

 During rising levels and in fairly stable conditions its contribu- 

 tions to Quiver Lake, and thus to the river, are practically nil. 



1896. 



(Table VI., PL XXXI.) 



There are 30 collections in this year, with a distribution 



