1915] Swezy: Binary and Muliiplc Fission in Hexamitus 73 



Material and Technique 



Occurrence. — Species of Hexamitus have been figured from a wide 

 variety of hosts, including nearly all species of Amphibia which have 

 been examined, as well as from fishes, snakes, tortoises, rats, and mice, 

 and it is quite probable that further investigations will reveal a still 

 greater number of hosts. One species, 77. inflatus, has been figured 

 from stagnant water. 



The observations which follow were based on examination of 

 Hexamitus from a variety of amphibians, Diemyctylus torosus Esch., 

 Aneides lugubris (Hallowell), Plethodon oregonensis Girard. Batra- 

 coseps attenuatus Esclis., Rana boylei Baird, 7?. draytoni Baird. all 

 obtained in and around Berkeley. California, and Rana pipiens Shreber 

 from Illinois. 



The region of infection has been the same in all the hosts examined, 

 the rectum and large intestine, with special concentration about the 

 point of .junction of the large and small intestine. The entire length 

 of the intestinal tract has been examined repeatedly, without showing 

 the presence of flagellates elsewhere, except those very probalily intro- 

 duced with the instruments used. 



Wet fixation for permanent preparations was used exclusively, hot 

 Schaudinn's fluid and Flemming's solution giving the best results. 

 Heidenhain's iron haematoxylin was u.sed for most of the work, though 

 many other stains were tried with varying results. 



Study of the living animal was made possible by sealing down the 

 cover glass with vaseline, after adding a few drops of normal salt 

 solution to the material from the intestine. Intra-vitam staining was 

 tried with neutral red, methylene blue N, new methylene blue GfJ and 

 Janus green, prepared with normal salt solution. 



In .spite of the wide range of hosts, one species, Hexamitus intesti- 

 nalis Du,]., seems to be the one commonly met with. It retains its 

 specific characters through all the great diversity of environmental 

 conditions. It is frequently the only protozoan found in the intestine 

 and is then generally present in vast numbers. Sometimes associated 

 with it, or .sometimes alone, are other species, or it may be only 

 varieties, which occur in much smaller numbers. The possibility of 

 these latter being only developmental forms of 77. intestinalis can be 

 decided, as in the case of the other flagellates considered, only after 

 an investigation of the complete life-cycle of these organisms has estab- 

 lished the fact that the life-cycle here is not a simple, direct one as 



