306 ROBERT A. BUDINGTON AND HELEN F. HARVEY. 



protoplasm of the line treated with thyroid was identical with 

 that of the control carried beside it. 



The procedure in any experiment was this: two protozoa of 

 common parentage were isolated, each in four drops of the same 

 culture medium. To one of the slides was added a minute mass 

 of pulverized gland, which would thus influence the protozoan 

 either as a food, or as a factor in the environing medium so far as 

 this acted as a solvent.^ The actual amount of each pulverized 

 gland thus used was small, and a like amount of each was deter- 

 mined as closely as possible by careful subdivision of a slightly 

 larger mass on a clean paper surface. To weigh out the powder 

 would give no more equal amounts, inasmuch as the glands are 

 so invaded by vascular and connective tissue that any moiety 

 taken might easily contain more or less of other than glandular 

 material. A slight amount of fresh hay infusion was added to 

 each slide each day, and the experiment continued six days or 

 more. The results given in this account are limited to those 

 obtained during the first six days only; to keep track of the off- 

 spring of even a single protozoan longer than this is extremely 

 difficult, as many know. The effect of each different gland was 

 tested by three trials. 



Circumstances were such that it was not always convenient 

 or possible to run experiments with all five different thyroids at 

 one time, so a control was carried along beside the gland-fed 

 individual in each case. This assured that the same conditions 

 of every sort attended both experimental and control lines, no 

 matter when the observations were made. If any circumstance 

 favored or interfered with either, the same was true for the other. 



Experimental Findings. 



The following tables show the exact results, so far as number 

 of individuals resulting from division of the original one goes, 

 this rate of cell division being the only index of thyroid effect at 

 present ready for presentation. The ciliate used in the first 

 series of experiments was Stylonichia; in the second and third 

 series we used Paramcecium. While the evidence is too limited 

 to permit any rigid conclusion of the kind, the data at hand seem 



^ Shumway states in his recent paper, loc. cit., that more or less of the material 

 thus offered Paramcecium is actually ingested and digested. 



