626 



FAMILY: CHILOMASTIGID^ 



be seen the group of blepliaroplasts, which are often more scattered than 

 in the flagellates themselves. 



The cytostomal cleft can be seen extending for the greater part of the 

 length of the cyst, while the flagellum can often be detected within it. 

 The cysts most usually remain in this condition, and are passed from the 

 body sometimes in large numbers, so that several can be seen in every 

 field of the twelfth objective. Though large numbers of the cysts have 

 been examined by the writer and other observers, no indication of nuclear 

 division has been noted. Kofoid and Swezy (1920), however, describe a 

 division process within the cyst. Division of the blepharoplasts is followed 

 by mitotic division of the nucleus, while the cytostomal cleft and the 

 marginal fibres are duplicated. There results a cyst containing a flagellate 



Fig. 258. — Cysts of Chilomastix mesnili with Two Nuclei: Six Nuclei in Various 

 Phases of Mitosis (x 3,500). (After Hegner, 1923.) 



with two sets of the various structures possessed by the ordinary cysts. 

 Division of the cytoplasm into two flagellates would presumably be the 

 next stage, but this was not observed. Hegner (19236) has also observed 

 binucleate cysts of C. mesnili, and has noted that the single nucleus divides 

 by mitosis in which about five chromosomes are present (Fig. 258). 

 Binucleate cysts are undoubtedly of rare occurrence, as no other observers 

 have seen them. 



G. mesnili is sometimes present in very large numbers in diarrhoeic 

 stools, both in the free and encysted condition. In formed stools only the 

 cysts are found. The persistence of the infections is well illustrated by a 

 case observed by the writer and O'Connor (1917) in Egypt, where C. mesnili 

 was continually present during an observation period of fifty days. In 

 another case it was present for ninety days, except for an interval of a 



