94 PROTOZOOLOGY 



tions. This is sometimes referred to as mixotrophic nutrition (Pfeif- 

 fer). For example, Euglena gracilis, according to Zumstein (1900) 

 and Lwoff (1932) may lose its green coloration and becomes Astasia- 

 like in the dark, or even in the light when the culture medium is very 

 abundant in decomposed organic substances, which may indicate 

 that this organism is capable of carrying on both holophytic and 

 saprozoic nutrition. 



With the introduction of bacteria-free culture technique in recent 

 years, it has now become well established that a protozoan species 

 exhibits conspicuous differences in form, size and structure, which 

 are exclusively due to differences in the kind and amount of food 

 material. For example, Kidder, Lilly and Claff (1940) noted in 

 Tetrahymena vorax (Fig. 38), bacteria-feeders are tailed (50-75ju 

 long), saprozoic forms are fusiform to ovoid (30-70iu long), forms 

 feeding on sterile dead ciliates are fusiform (60-80ju long), and carni- 

 vores and cannibals are irregularly ovoid (100-250^ long), in the 

 latter form of which a large preparatory vacuole becomes developed. 

 In Chilomonas Paramecium, Mast (1939) observed the individuals 

 grown in sterile glucose-peptone solution were much smaller than 

 those cultured in acetate-ammonium solution and moreover the 

 former contained many small starch grains, but no fat, while the 

 latter showed many larger starch grains and a little fat. Amoeba 

 proteus when fed exclusively on Colpidium, became very large and 

 extremely "fat" and sluggish, growing and multiplying slowly, but 

 indefinitely; when fed on Chilomonas only, they grew and multi- 

 plied for several days, then decreased in number and soon died, but 

 lived longer on Chilomonas cultured in the glucose-peptone. 



Since the fact that endocrines influence greatly the metabolic ac- 

 tivity and growth in higher animals became known, many workers 

 undertook to determine the effects of various endocrines of verte- 

 brates upon Protozoa. Nowikoff (1908) first noticed the apparent 

 increase in number of Paramecium caudatum when cultured in a solu- 

 tion of desiccated sheep thyroid as compared with the culture in a 

 hay infusion. Shumway (1914, 1917) found that the emulsions of 

 fresh thyroid, boiled thyroid and commercial powder, produced an 

 increase of about 65 per cent in the division rate in Paramecium over 

 common hay infusions. These animals were smaller and more ac- 

 tively motile, and showed more vacuolated cytoplasm. Abderhalden 

 and Schiffmann (1922) made a similar observation by using thyroid 

 "optone." Shumway found further that suspensions of thymus, 

 spleen, ovary, suprarenal, and pituitary body, did not have any ef- 

 fect on Paramecium. By using freshly prepared thyroid extracts of 



