THE EFFECTS OF A THYROID DIET UPON 

 PARAMAECIUM 



WALDO SHUMWAY 



From the Department of Biology, Amherst College 



TWELVE FIGURES 



CONTENTS 



Introduction ' 529 



Methods 531 



History of the races 532 



Feeding experiments 536 



a. On the A race 536 



b. On the B race 541 



c. On the C race 547 



The effect of the thyroid 549 



a. Oh the division rate 549 



b. On the gastric vacuoles 554 



c. On the contractile vacuoles 555 



d. On the non-contractile excretory vacuoles 557 



e. On monstrosities 560 



f. General 561 



Summary and conclusions 561 



Literature cited 562 



INTRODUCTION 



The classical investigations of Maupas ('88-'89) upon the life 

 cycle of Paramaecium, with the subsequent researches of Calkins 

 and of Woodruff, have established the value of the division-rate 

 as an index to the vitality of pedigreed races. Calkins ('15) con- 

 cludes, ''that more or less definite cycles of vigor or depression, 

 ending in natural death unless conjugation or its equivalent su-. 

 pervenes, are characteristic of all pedigreed races of infusoria." 

 It has been shown by many investigators that this life cycle, as 

 indicated by the division-rate is readily influenced by environ- 

 mental changes, i.e., in the temperature, amount or kind of food 

 present, or chemical composition of the culture medium. 



529 



