562 * WALDO SHUMWAY 



control lines, and the thyroid produces the greatest acceleration 

 of the division rate when the control line is dividing most 

 rapidly. 



6. Paramaecia ingest and digest particles of the thyroid. 



7. There is no significant difference between the number of 

 gastric vacuoles formed in a given time between the thyroid fed 

 and the control Paramaecia. 



8. There are profound disturbances of the excretory system 

 in the thyroid fed Paramaecia. The most remarkable of these is 

 an increase from two to three contractile vacuoles. 



9. The thyroid fed Paramaecia manifest at all times a highly 

 vacuolated protoplasm, such as has been described for starved 

 Paramaecia, even during their periods of most rapid division. 

 It has been shown that these large vacuoles are to be considered 

 non-contractile excretory vacuoles. 



10. It is suggested that the results of thyroid feeding here 

 noted are due to the presence of a remarkably stable hormone 

 in the thjToid which may be classified among the ' dissimilatory' 

 hormones. 



LITERATURE CITED 



BiEDL, A. 1913 Innere Sekretion, pp. 252, 253. 



BuDiNGTON, R. A. AND Harvey, H. F. 1915 Division rate in ciliate Protozoa 



as influenced by thyroid constituents. Biol. Bull., 28, 5. 

 Calkins, G. N. 1902 Studies on the life history of Protozoa I. Arch. f. Ent- 



wick., 15, 1. 



1904 Studies on the life history of Protozoa. IV. Jour. Exp. Zool., 



1, 3. 



1915 Cycles and rhytlims and the problem of 'immortality' in Para- 



maecium. Am. Nat., 49, 578. 

 Calkins, G. N. and Lieb, C. C. 1902 Studies on the life history of Protozoa. 



III. Arch. f. Prot., 1, 1. 

 DoBELL, C. 1914 A commentary on the genetics of the ciliate Protozoa. Jour. 



Gen., 4, 2. 

 EsTABROOK, A. H. 1910 Effect of chemicals on growth in Paramaecium. Jour. 



Exp. Zooh, 8, 4. 

 GuDERNATSCH, J. F. 1912 Feeding experiments on tadpoles I. Arch. f. Ent- 



wick., 35, 3. 



1913 Feeding experiments on tadpoles II. Am. Jour. Anat., 15, 4. 

 Hance, R. T. 1915 The inheritance of extra contractile vacuoles in an un- 

 usual race of Paramaecium caudatum. Science, n.s., 42, 1083. 



