96 PROTOZOOLOGY 



rate in P. putrinum occurred only in faintly alkaline thyroid ex- 

 tract in hay infusions. Riddle and Torrey (1923) on the other 

 hand found that the thja-oxine brought about a slight fall in the 

 rate of division, an increased rate of pulsation of the contractile 

 vacuoles, and a decrease in number of excretory crystals in Para- 

 mecium. The two investigators suggested that the thyroxine acceler- 

 ates catabolic, and not anabolic, processes. Woodruff and Swingle 

 (1923, 1924), using a pedigree culture of P. aurelia found that (1) 

 neither thyroid, pineal, nor pituitary material possesses intrinsic 

 properties which accelerate division in Paramecium and (2) thyrox- 

 ine does not accelerate the division and above certain concentrations, 

 it depresses the division in this ciliate. 



Ball (1925) found different clones of P. caudatum and P. aurelia, 

 respond differently to similar conditions and obtained following re- 

 sults: (1) with an uncontrolled bacterial food supply, individuals of 

 the same clone may divide at a higher rate in solutions of the desic- 

 cated thyroid, liver, and hypophysis, than in hay infusions; (2) if ap- 

 proximately equal number of bacteria are provided, thyroid does not 

 bring about any significant increase in the division rate; and (3) the 

 evidence indicates that thyroid accelerates the division rate of 

 Paramecium by providing a favorable bacterial food supply, and 

 not by any specific action of the thyroid hormone. Solutions of both 

 the anterior and the posterior lobes of the pituitary gland produce 

 no significantly higher rate of division than does a solution of liver. 

 Unlike the observations made by some previous workers. Ball finds 

 no demonstrable increase in the metabolic rate in thyroid-fed ani- 

 mals as compared with those cultured in hay infusions. 



The importance of vitamins has abundantly been demonstrated 

 in recent years for many higher animals. It is, therefore, natural to 

 find attempts made to discover the influence of certain vitamins on 

 Protozoa. Lwoff and Dusi (1937, 1938) found the growth of Chilo- 

 monas Paramecium in asparagin media was favorably supported by 

 thiamine, or by thiazole, and in ammonium acetate media, thiamine 

 could be replaced by thiazole and pyrimidine. Thiamine has no ac- 

 celerating effect on the growth of Euglena gracilis in light (Elliott, 

 1937), but either this substance or pyrimidine is necessary for the 

 growth of the organism if cultured in asparagin and acetate media in 

 darkness (Lwoff and Dusi). It is probable that chromatophore-bear- 

 ing forms are able to synthesize thiamine from the constituents of 

 inorganic media in sunlight. E. pisciformis on the other hand is said 

 to require thiamine for growth even in light (Dusi, 1939). 



Many colorless flagellates require thiamine for growth as in Chilo- 



