112 PROTOZOOLOGY 



Soon a large number of observers came forward with varying re- 

 sults — some confirmatory, others contradictory. The vast majority 

 of these observations including Robertson's own, were carried on 

 ciliates which were grown in association with various bacteria, and 

 naturally, the results lacked agreement. For a review of these ob- 

 servations too numerous to mention here, the reader is referred to 

 Allee (1931, 1934), Mast and Pace (1938) and Richards (1941). 

 When bacteria-free cultivation became possible for some Protozoa, 

 it was hoped that this problem might be solved under controlled 

 conditions. How r ever, the results still lack agreement. For example, 

 Phelps (1935) reported that in Tetrahymena (Glaucoma), the 

 growth rate and the maximum yield were the same between tw r o 

 cultures: one started with 0.014 organism and the other, with 1600 

 organisms per ml. Thus there was no allelocatalysis. On the other 

 hand, Mast and Pace (1938) noted a significant acceleration of the 

 growth rate in Chilomonas when up to 50 organisms were inoculated 

 into 0.4 cc. of culture fluid as compared to the growth rate in cultures 

 with one or more Chilomonas inocula, and furthermore, a single 

 Chilomonas showed an increased rate of reproduction as the volume 

 of the culture fluid was reduced. 



Various aspects of metabolic processes in Protozoa such as inor- 

 ganic requirements, carbon and nitrogen metabolism, growth fac- 

 tors, vitamins, etc., have recently been studied by a number of in- 

 vestigators. For information, the reader is referred to Hall (1941) 

 and Lwoff (1951). 



Reserve food matter 



The anabolic activities of Protozoa result in the growth and in- 

 crease in the volume of the organism, and also in the formation and 

 storage of reserve food-substances which are deposited in the cy- 

 toplasm to be utilized later for growth or reproduction. The re- 

 serve food stuff is ordinarily glycogen or glycogenous substances, 

 which seem to be present widely. Thus, in saprozoic Gregarinida, 

 there occur in the cytoplasm numerous refractile bodies which stain 

 brown to brownish-violet in Lugol's solution; are insoluble in cold 

 water, alcohol, and ether; become swollen and later dissolved in boil- 

 ing water; and are reduced to a sugar by boiling in dilute sulphuric 

 acid. This substance which composes the refractile bodies is called 

 paraglycogen (Biitschli) or zooamylon. Gohre (1943) considers it a 

 stabilized polymerization product of glycogen. 



Rumjantzew and Wermel (1925) demonstrated glycogen in Ac- 

 tinosphaerium. In the cysts of Iodamoeba, glycogen body is con- 



