EFFECT OF THYROID ON DIVISION RATE OF 

 PARAMAECIUM 



WALDO SHUMWAY 



From the Zoological Laboratory, Columbia University 



THREE FIGURES 



INTRODUCTION 



The remarkable results recently described (Gudernatsch 

 '12, '13) of a thyroid diet upon the development of the tad- 

 pole suggests interesting problems as to the effect of this sub- 

 stance upon the individual cell. In the following paper is given 

 an account of the effects observed on the life history of Para- 

 maecium aurelia when particles of thyroid were added to its diet. 

 The experiments here described were carried on in the Zoological 

 Laboratory at Columbia University and in the Marine Biological 

 Laboratory at Woods Hole, under the direction of Prof. Gary N. 

 Calkins, to whom the writer's thanks are due for encouragement 

 and advice. 



In studying the effects of chemicals on Paramaecium, many 

 different indices have been employed by previous writers, espe- 

 cially chemotaxis, size, division-rate, and the phenomena ex- 

 hibited by the gastric vacuoles. The rate of division has been 

 chosen in these experiments as an index of the effects produced 

 by the thyroid, as the investigations of Calkins, Woodruff and 

 others have shown that it is very greatly affected by slight 

 changes in the environment. Very recently Woodruff and Un- 

 derbill have used this method in their series of investigations 

 on "Protozoan Protoplasm as an Indicator of Pathological 

 Changes" ('13-'14). 



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