XVI 



PAGE 



Effect of temperature fluctuations on plankton 474 



In early spring of 1896 475 



In late autumn of 1897 476 



Exceptional high production at minimum temperatures 476 



Effect of autumnal decline in temperatures 477 



Effect of temporary heat pulses 477 



Effect of the winter ice-sheet 479 



Light and plankton production 480 



Imperfection of data 480 



Production in periods of greater and less illumination 480 



Production in clear and turbid waters 481 



Production in clear and cloudy weather 482 1 



Vegetation and plankton production 483 



Greater production in vegetation-poor lakes 484 



Comparison of monthly means of production in lakes rich and poor 



in vegetation 484 



Seasonal changes in vegetation and in relative production 485 



Combination of other factors with vegetation to depress production 486 



Current and tributary water 487 



Chemical conditions 488 



Corroborative evidence from Matanzas Lake 489 



Production in Quiver and Dogfish lakes in years of much and little 



vegetation 491 



Depression of production during dominance of submerged veg- 

 etation 493 



Production in vegetation-rich waters of Flag Lake 494 



Emergent vegetation a source of enrichment 494 



Struggle for existence between submerged flora and phytoplank- 



ton 496 



Chemical conditions in the two types of lakes 497 



Impoverishing effect of submerged vegetation 499 



Obstructive effect of submerged vegetation 499 



Effect of vegetation on constitution of plankton 500 



Effect of vegetation on fish production 501 



Experiment suggested 502 



Internal factors and plankton production 502 



Normal regimen of plankton production 503 



No seasonal regularity in amplitude of production 504 



Rank of different stations in production more stable 504 



Degrees of stability in different localities 505 



Is there a normal sequence in production? 506 



Direction of movement in mean monthly production 507 



Predominant seasonal changes in direction 507 



The cyclic movement of recurrent pulses 509 



Necessity of brief interval of collection 5°9 



Suggestions of cyclic phenomena in data of other investigators 509 



Evidence in our records 5 I0 



Cyclic movement defined 510 



