410 PROCEEDINGS OF THE ACADEMY OF [July, 



SOME EFFECTS OF ENVIRONMENT ON THE GROWTH OF LYMN^A 

 COLUMELLA Say.^ 



by harold sellers colton. 

 Table of Contents. 



PAGE 



I. Introduction 410 



II. Historical 411 



III. Materials 412 



Natural History 413 



Description of Dwarfs 414 



IV. Methods 415 



Precautions 416 



Measurements 417 



Description of Tables 418 



Analysis of Experiments 418 



V. Experiments on Growth of Lymnita 420 



1. Food: Water Plants...^ 420 



Effect of Sediment 423 



Effect of Fa?ces 425 



Other Effects of the Water Plants .' 425 



2. Aeration 425 



De Varigny's Experiment 426 



Willem's Experiment 426 



Effect of Surface Aeration 426 



Efifect of -Artificial Aeration 428 



3. Composition of the Water 430 



Effect of Accumulation of Excreted Matter 430 



Effect of Shell Salts 434 



Effect of Number of Individuals 434 



4. Temperature 435 



5. Light 437 



6. Area 438 



7. Volume 440 



8. Alternation of Conditions 441 



9. Experiments on Tadpoles 441 



VI. Effect of External Conditions on the number of eggs laid 443 



1. Sediment 443 



2. Number of Individuals 444- 



3. Light 444 



4. Other Effects and Observations 445 



VII. Summary and Conclusions 446 



VIII. Literature 447 



I. Introduction. 



It is a widely recognized fact that animals raised in confinement 

 differ in various ways from those in the wild state. The differences 



1 The writer takes great pleasure in thanldng Dr. J. Percy Moore and Dr. E. G. 

 Conklin in particular for many helpful suggestions and criticisms in carrying out 

 the work. 



