320 L. R. CLEVELAND. 



not possible to note any change in their protozoa. Perhaps 

 Trichonympha takes the place of Trichomonas, but if this occurs, 

 it cannot be detected because there are so many Trichonympha 

 anyway. The loss of Trichomonas is of no consequence. 



(5) Termites with Leidyopsis and Streblomastix. Leidyopsis 

 multiplies in this group as in group (i), and perhaps takes the 

 place of Trichomonas as it does of Trichonympha. These ter- 

 mites, as those in group (i), are able to live indefinitely. Since 

 Streblomastix, as group (3) shows, is of no value to its host, we 

 may conclude that Leidyopsis alone, without the modicum of 

 assistance from Trichomonas such as it received in group (i), 

 is able to keep it shost alive indefinitely. 



(6) Termites with No Protozoa. These termites eat wood just 

 as those in the other five groups, but are not able to live longer 

 than three to four weeks. The inability to maintain themselves 

 on their normal diet of wood is caused by the removal of the 

 intestinal flagellates, particularly Trichonympha and Leidyopsis, 

 from them. 



DISCUSSION. 



Intestinal protozoa must live in an environment with a smaller 

 percentage of oxygen than their hosts, and should, therefore, 

 experience the greater difficulty when the oxygen environment 

 of the host is raised from 20 to 100 per cent., provided, of course, 

 the oxygen percentage of the parasite's environment does not 

 increase correspondingly with that of its host. For instance, if 

 there is normally, say, I per cent, of oxygen in the parasite's 

 environment and 20 per cent, in that of the host, when the host 

 is placed in an atmosphere of 100 per cent., the percentage of the 

 host's environment is thus increased only five times, while that 

 of the parasite is increased eighty times. On the other hand, 

 if the oxygen percentage of the parasite's environment increases 

 correspondingly to that of its host, or, as in this case, five times, 

 then the parasite would be in 5 per cent. oxygen when its host 

 was in 100. When termites are placed in 100 per cent, oxygen, 

 the oxygen percentage of their parasite's environment may be 

 increased much more than their own, and the parasites are killed, 

 just as any animal would be with so great an oxygen increase. 

 If this is true, the parasites can undergo as great change in 



