58 SURVEY OF INVERTEBRATES 



ent time, to reach any definite conclusion concerning the 

 oxygen relationships of Trypanosomidae inside the in- 

 sect intestine. 



Regarding the intestinal stages of gregarines, only a 

 single observation is available. Von Brand (1943) 

 showed that the trophozoites of Gregarina steini, G. 

 cuneata and G. polymorpha — all three parasitizing the 

 intestine of Tcnebrio molitor larvae — stayed alive for 16 

 hours when the hosts were exposed to strictly anaerobic 

 conditions. Longer observation was unfortunately not 

 possible since the mealworms died after 24 hours. How- 

 ever, after 16 hours the gregarines were perfectly nor- 

 mal, and although counts were not made, no noticeable 

 decrease in numbers seemed to have occurred. This is of 

 some interest in view of the different behavior of Tri- 

 cJionympha mentioned above and would seem to convey 

 a hint that the gregarines are quite well adapted to 

 anaerobic life. Since these organisms cannot be cultured 

 and since the hosts are not very resistant to lack of oxygen 

 the progress of research on this point will probably be 

 slow and difficult. 



3. BLOOD AND TISSUE PROTOZOA 



Our knowledge of the anaerobic functions of the pro- 

 tozoa inhabiting the blood stream is extremely rudimen- 

 tary. These protozoa are probably not well equipped for 

 withstanding complete lack of oxygen since their normal 

 surroundings are obviously rich in oxygen. 



Von Brand (1933) found that the blood-forms of try- 

 panosomes survived only a few hours in anaerobic sur- 

 roundings and Wendel (1943) was able to maintain ma- 

 laria parasites alive under analogous conditions for only 

 an hour or two. It is a curious fact, to be discussed in 

 detail later, that, despite the easy availability of oxygen 

 in their normal surroundings, the normal metabolism of 

 trypanosomes and malaria parasites is characterized by 

 incomplete oxidations. 



