TOXICITY OF OXYGEN* FOR PROTOZOA. 463 



lenamorpha is killed in approximately thirty hours. It is 

 impo>sible to >uy \\ hether this difference in oxygen toxioity is due 



nvironim-nt or metabolism. Here is an interesting situation, 

 calling f<>r <M refill investigation. 



5. Goldfish and Salamanders. 



After h.i\ in^ r moved all protozoa from an air breathing coll- 

 bloodrd \rMi-brau-, the frog, it seemed expedient to oxygenate 

 a \\atrr bn-athing vertebrate harboring many protozoa. Gold- 

 fi-h and -alainanders (Nectiirus} were used for this purpose. 

 T\\ my yung goldfish, harboring large numbers of inu-stinal 

 the genus Hexamitns, and ten young salamandt i -. 

 hail. 01 in- large numbers of intestinal flagellates of the genera 

 1 n and Prou'azekella, were oxygenated at 3.5 atmos- 



plu res. I In- same thing occurred here as in the oxygenation of 

 :iaint 1\ . -ome hosts lost their protozoa sooner than otlit'i-: 

 Ilf\>:tnitns in some goldfish was killed in 4 hours and in otlu i> 

 not until 5 hours; Trictwnwnas and Prou'azekella in some sala- 

 maii'lti- \\tir killed in 9 to IO hours and in others not until 11 

 t" u lu>m-. In adult hosts it would probably take slightly 

 longer in kill all protozoa in all hosts. In the material used in 

 thi> >tu<ly all individuals of Trichomonas and Prowazekelln were 

 killttl in all hosts in u hours and all individuals of llcxnniitns 

 in all !ii>-t- in 5 hours, while the hosts were not killed before 50 



In do llnlirS. 



It i> intt it sting to note how closely these death points of 

 Hi ami Trichomonas inhabiting the water luvaihiiiL; 



vertebrates, -alamanders and goldfish, parallel those of the 

 //(.V(/m////.v and Trichomonas that inhabit the air breathing 

 \ (i tebrate, tin- frog (see Table II). 



It i- ipiitf | n<. liable that the external parasitic t iliato of fish 

 \\iiiilil In killetl b\- oxygenation and without injury to the li>h. 

 ami other j)rotozoan parasites, according to reports, do 

 bK- ilania^f to fish, which oxygenation would probably 

 check. 



What eftert o\\;^i-nation would have on the hundreds of species 

 of ^I'oro/oa in ti-lu - -Imuld be determined. 



