PROTOZOA AND OTHER ANIMALS 971 



Protozoa of Zootertnopsis, not the maximum period of survival of the 

 termites. Cornstarch caused death of the Protozoa and the termites after 

 twenty-three days; the starch was apparently in granular form. (In com- 

 parison with Montalenti's results, light may be thrown on the discrepancy 

 by the statement of Ullmann (1932) that invertebrates are unable to use 

 the starch of the plant food, but that soluble cooked starch is very well 

 digested by all animals.) Lund used a variety of carbohydrates, on most 

 of which the maximum survival of both Protozoa and termites did not 

 greatly exceed the effects of starvation; and on some they died more 

 quickly. On inulin, dextrin, and lactose Trichomonas and Streblomastix 

 were living in the last termites reported at forty-eight, forty-four, and 

 sixty-five days. Cleveland (1925c) found that Trichomonas (accom- 

 panied by Streblomastix) can keep the host alive from forty to fifty 

 days longer than when no Protozoa are present, but "very few if any 

 [termites] were able to live indefinitely." The hypermastigotes are most 

 important in the mutualistic symbiosis in Zootermopsis. 



Cleveland et al. (1934) studied the effects of various diets on Crypto- 

 cercus punctulatus and its Protozoa, using various cellulose-free carbo- 

 hydrates, peptone, gelatin, and glycogen. On no substance did any ex- 

 cept the smaller polymastigotes survive very long; nor did the roaches 

 live more than a few days longer than when water alone was given. 

 These authors found that dextrose is of more food value than the other 

 substances, and considered it likely that a diet including dextrose might 

 be found upon which the insects could live for a long time, if not in- 

 definitely, without Protozoa. 



Dextrose prolonged the survival period also of defaunated Reticu- 

 litermes flavipes (Cleveland, 1924). Trager (1932) demonstrated dex- 

 trose in the presence of extract from the hind-gut contents of Crypto- 

 cercus. Cleveland et al. (1934) suggested that dextrose, produced from 

 cellulose by the action of ccllulase and cellobiase in the cytoplasm of 

 the flagellates, insofar as it is not used in their metabolism or stored as 

 glycogen, diffuses from their bodies. Hungate (1939), however, identi- 

 fied acetic acid, carbon dioxide, and hydrogen as metabolic products of 

 the Protozoa; and thought it likely that most of the sugar resulting from 

 their digestive processes undergoes anaerobic dissimilation by the Proto- 

 zoa. According to this view, the termites would make use of the acetic 

 acid. 



