1915] Swezij: Binanj and Multiple Fission in Hexamittis 77 



rence in these flagellates has not heretofore been described as multiple 

 fission, yet multinucleate forms, the product of multiple fission, are 

 almost as frequently met with in smears from the intestinal wall as 

 are stages in binary fission. 



The process of multiple fission is accomplished by quickly repeated 

 mitoses without synchronous division of the cytoplasm, thus resulting 

 in a multinucleated plasmodium or somatella. Following the first 

 division of the nuclei and the completion of the attendant organelles, 

 the second division is initiated in the same way by the splitting of the 

 blepharoplasts and axostyles (pi. 10. fig. 16). The next step, the 

 moving apart of the blepharoplasts to take up polar positions 180° 

 apart on each nucleus (pi. 10. fig. 17), is identical with the correspond- 

 ing process in binary fi.ssion (pi. 9, fig. 4), save only in the increased 

 number of nuclei in the organism as a whole. 



The third division, giving rise to the nuclei and extranuelear 

 organelles adequate for eight individuals, was not followed out fully. 

 Figure 18, plate 10, with its ten nuclei, representing five individuals, 

 shows that it had taken place in the earlier history of that somatella. 



Division of the somatella. or plasmotomy, consists in the liberation 

 of one individual at a time, in the manner described for the tricho- 

 monacls (Kofoid and Swezy, 1915&). 



The flagellates move about actively throughout the whole process 

 of multiple fission. No evidence has been found thus far to indicate 

 that multiple fission ever takes place while the flagellate is encysted. 

 The constant lashing about of the flagella gives to the organism some- 

 thing of the rolling motion of Volvo.r. There seems to be no constant 

 appreciable increase in size of the forms undergoing multiple fission 

 as compared with those dividing by simple binary fission. 



Hexamitus batrachorum sp. nov. 



This flagellate is often present in the greatest abundance, and 

 frequentl.v individuals of this species may be found in hosts where the 

 predominating species is one of the larger forms like H. intestinalis, 

 though this is not always the case. 



It has occurred in Rana pipiens, in Batracoseps aftcnuatus and 

 sparingly in the other amphibians examined. It resembles, in its 

 nuclear structure, a Hexamitus figured by Alexeieff (1912) from a 

 tortoise, Nicoria trijvga, in Ce.vlon, which he designates as H. parvus. 

 His figures are accompanied by no description, however, but seem to 



