1915] Swe<y: Binary and Mulfiph Fission in Hvxaniitus 81 



plast complex. What special significance these may have could not 

 be determined. Their persistence in degenerated forms where the 

 cytoplasm has entirely disappeared would suggest that they were not 

 mere protoplasmic vacuoles (pi. 11, fig. 41). 



No differentiation of the cytoplasm into ectoplasm and endoplasm 

 has been observed, the body being covered, apparently, by a very thin 

 periplast. 



Binary Fission 



Binary fission in H exam it us intestinalis follows the same general 

 process already outlined for H. ovatiis. The early prophase shown in 

 figure 28, plate 11. shows the completion of the splitting of the ble- 

 pharoplasts, axostyles and posterior flagella and the beginning of the 

 migration of each daughter group to opposite poles of the nucleus. 

 The great diminution of the chromatin material in the blepharoplast 

 complex is even more striking here than in H. ovatus. The early 

 prophase shown in figure 29, plate 11, where the large mass of chromatin 

 is broken up and only a few granules remain in the nucleus, may or 

 may not have some significance in the process, though it is hard to 

 correlate it with the earlier and later stages. It is quite probable that 

 it is the result of some abnormality or some phase of degeneracy. 



The apparent lack of a nuclear membrane is here quite striking, 

 the spindle evidently lying entirely free in the cytoplasm (pi. 11. figs. 

 30, 31). 



Here, as also in H. ovatus, multiple fission is a common mode of 

 multiplication at some period in the life cycle (pi. 11, figs. 37. 38, 39) 

 and probably results in a somatella of eight pairs of nuclei, i.e., poten- 

 tially eight trophozoites. 



Discussion 



The first attempts to portray this process of multiple fission in 

 Hexamitus were made by Poa (1904) and Wenyon (1907). but a few 

 stages only were figured. These agree with certain stages abundant 

 in my own preparations. Dobell (1909) refers to the figures given 

 by these investigators as "merely degenerate and fused forms which 

 have nothing whatever to do with division." His own explanation of 

 division as consisting of the absorption of both axostyles and caudal 

 flagella, the division of the nucleus and the appearance of new axostyles 



