SYMBIOSIS BETWEEN TERMITE AND FLAGELLATES. 315 



which is thus enabled to live considerably longer than its proto- 

 zoa. In nature, termite protozoa may aid their host by giving 

 themselves as food. It is not known how long the life-cycle of 

 these protozoa is, but, if it is not longer than that of the parasitic 

 protozoa that have been cultivated in artificial media from a 

 single individual, countless millions of them must die daily in a 

 single termit 



b. Oxygenation. 



It has been fairly common knowledge for some time that 

 i^en in rather excessive or abnormal amounts is toxir t<>t 

 many, if not all, forms of animal life. Realizing there must be 

 \ery little n in the environment of intestinal protozoa, 1 



concluded that they might for this reason be more sensitive to 

 it than tlu-ir lio-t in an atmosphere of approximately 20 per cent, 

 oxygen. A< ' ' "idingly, it was decided to determine \\hether 

 oxygen \\a> more toxic for intestinal pura-ites than for their 

 In.-i. < )1>\ iou>ly, for many reasons, termite-- are far superior to 

 .my other inject and perhaps any other animal for such a study. 

 Workers, >oldiers, and nymphs of the repn>du< ti\ e caMe>. tan 

 oimti-d <ni to have an infection of 100 per cent., approximately 

 tin- -ame in all indi\ idlials of the same size and age. And there 

 are million- of \ ci \ large, active and highly -peciali/ed flagellates 

 in a j-ingle insect. In fact, nearly half the body weight of the 

 in-rt I i> made up of these protozoa. Where, then, could a 

 better opportunity be found to study the effect of oxygen on 

 intestinal flagellates? The termites are easily kept in the labora- 

 tor\ and will li\e almost indefinitely in tightly nuked \ials and 

 tla-k-, for the\ an -land a very high pen > -nta^e of ('O 2 . 



The-e experiiiu-nts were begun with a different end in view 

 from the u-r that is made of them in thi> paper, for it was not 

 thought that all the intestinal protozoa could be removed without 

 injuring the termites too, and still less wa- the possibility con- 

 templated that oxv^-ii might entirely remo\t- -ome genera of 

 HUM- flav;i-llati> before killing others. The other subject, th.it 

 of the toxicity of oxygen proper, is being studied now and will 

 be taken up in detail in a later paper. 



It was found that if termites (Termopsis) were placed in fairly 

 pure oxygen at one atmosphere pressure that all protozoa be- 



