EFFECTS OF THYROID ON PARAMAECIUM 



557 



While an increase in the number of contractile vacuoles was 

 the most striking effect produced by the thyroid on the excre- 

 tory system, other derangements of greater or less importance 

 have been observed. In the forms with three vacuoles the ap- 

 paratus of each has appeared normal, as has been the rate of 

 pulsation. In thyroid treated individuals with but two vacuoles, 

 however, there have always been abnormalities of some sort 

 present. In some cases these appear as an increased rate of 

 pulsation, in others as an increase in the number of feeding 

 canals to from eight to ten, whereas the normal number is five or 



Fig. 7 Paramaecium caudatviin after 180 days thyroid treatment, showing 

 three contractile vacuoles. Drawn from life. 



Fig. 8 Paramaecium caudatum after 180 days thyroid treatment, showing 

 three contractile vacuoles. Drawn from life. 



six. In still others the feeding canals, instead of forming a star 

 around the vacuole, are greatly elongated to form systems 

 stretching the extent of the cell. 



These abnormalities occurring in the excretory system of the 

 thyroid fed line of the C race throughout its history and ranging 

 from slight increases in the rate of pulsation to structural changes 

 involving the production of supernumerary apparatus can only 

 indicate a greatly increased rate of excretion. 



d. On the non-contractile excretory vacuoles. Calkins ('04) in 

 describing the degeneration changes in the protoplasm of Para- 

 maecium during depression periods notes the appearance in the 

 endoplasm of large shining vacuoles ('starvation vacuoles' of 



