1915] Sivezy: Binary and MuUipIc Fission in Hexamitus 79 



can be seen to pass over or under the nuclei to reach the blepharoplasts, 

 and seem in no way to be connected with the nuclei. 



The cytoplasm is granular, sometimes more or less vacuolated, and, 

 in general, contains no food inclusions other than fluid-filled vacuoles. 



Fission 

 The process of fission, binary and multiple, was not observed be- 

 yond the occurrence of numerous forms which showed that multiple 

 fission takes place here as well as in the other species described. The 

 forms noted (pi. 10, figs. 22, 23) are similar to the corresponding stages 

 of H. ovatus and H. intesfinalis. 



Hexamitus intestinalis Dujardin 



This is a variable form both as to size and general appearance, and 

 yet it is quite evident from an examination of the figures given by 

 different investigators that more than one species has been described 

 imder this name. 



Morphology 



Hexamitus intestinalis varies in size from 9 to 12/n in length and 

 5 to 8^ in width, though forms both above and below these limits are 

 occasionally met with. In general outline the body is ovoidal, taper- 

 ing more or less toward the posterior end (pi. 11, fig. 25), which may 

 occasionally be metabolic in its appearance (pi. 11, fig. 27). Individ- 

 uals are frequently met with which are rounded at the posterior end 

 (pi. 11. fig. 26), thus showing three quite distinct bodily forms or 

 changes. In hosts where the rounded, oval individuals are present 

 the majority of the flagellates seem to belong to that type. When 

 forms having the posterior extremity metabolic are found that type 

 will be predominant in the preparations made, and the same thing is 

 true of the third type with pointed posterior end. These changes 

 do not seem to indicate any specific difl'erentiation, but are rather 

 different responses of one species to changes of medium, due to .slight 

 environmental changes. This, however, is merely a suggestion from 

 observations. No attempt has been made to prove it by experiment. 



The three pairs of flagella arise at the anterior end from two pairs 

 of basal granules, the central ones of which may become fused and 

 appear as one granule (pi. 11, fig. 25). One flagellum arises from each 

 of the outermost granules and two flagella from each of the inner 



