INTESTINAL FLAGELLATES OF RATS 133 



stancy of the chromosomes in T. muris indicate that the mechan- 

 ism for the qualitative division of the physical basis of heredity 

 is as precise as it is in the higher animals and plants. Since the 

 karyosome disappears during mitosis, to form again after nuclear 

 division, a certain amount of nuclear reorganization must accom- 

 pany each division. Perhaps this reorganization may serve to re- 

 vitalize the nucleus making syngamy unnecessary. 



Multiple fission has been described for T. muris by Kofoid and 

 Swezy (1915) and consists of successive duplications of the 

 nucleus and other organelles without immediate plasmotomy. This 

 leads to the production of smaller individuals than those produced 

 by binary fission, as many as eight individuals having been seen 

 in one "somatella." This process seems to be of rare occurrence 

 and has been seen only once by the writer. The significance of 

 multiple fission is obscure. One is tempted to think of the forma- 

 tion of gametes {T. uiinutaf) in this manner but evidence of 

 syngamy is entirely wanting, at present. 



Adequate accounts of fission in Cliiloniastix bettencourti are 

 lacking. Some details have been worked out for division of C. nies- 

 nili in the cysts (Kofoid and Swezy, 1920; Hegner, 1923^) and 

 for the active stages of C. aidostomi (Belar, 1921), C. magna 

 (Becker, 1926c) and of C. gaUinanim (Boeck and Tanabe, 1926). 

 The details of division within the cysts and that of the active 

 state differ considerably and further studies should be made to 

 determine all the facts and their adequate interpretation. 



In Hcxamitus muris binary and sometimes multiple fission takes 

 place in the active state or within the cyst. Some stages are given 

 by Wenyon (1907) but full details have not been described, for 

 this species or for H. pulcher. Alexeieff (1911&) gives some stages 

 in the division of H. pulcher from Triton cristatus but the most 

 complete accounts in this genus are those of Swezy (1915) for 

 Hcxamitus ovatus and of Davis (1926) for Octomitus (Hcxa- 

 mitus f) sahnonis. In each case intranuclear spindles with chrom- 

 osomes are described. 



Binary fission has been described in some detail for Giardia 

 muris by Kofoid and Christiansen (1915&), for G. microti by 

 Boeck (1917) and for G. cntcrica (lainblia) by Kofoid and Swezy 

 (1922). In each case nuclear division within the parental nuclear 

 membrane and the formation of four chromosomes and their 

 division on a spindle were described. The axostyles appear to 



