122 



BIOLOGY OF THE PROTOZOA 



similar, although the number of chromosomes is usually smaller. 

 Thus Kofoid and his collaborators found about 24 in Leidyoysis 

 sphcerica, 12 in Trichomiius iermitidw, and 4 in Giardia mnris 

 (Fig. 140, p. 293). 



D 



E 



B 



C 



Fig. 63.- — Monocystis rostrata chromosome reduction. A, Formation of spindle 

 in pseudo-conjugant; B, C, nuclear plates of progamous divisions, 8 chromosomes; 

 D, anaphase of same; E, anaphase of last progamous division, the number of chromo- 

 somes is here reduced from 8 to 4. (After Mulsow.) 



A small nmnber of chromosomes is likewise found in a number 

 of the Gregarinida, and their history in division approaches that of 

 metazoan chromosomes. Thus in the case of Monocystis rostrata 

 Mulsow describes 8 definite chromosomes formed from a portion of 

 the nuclear chromatin, the nmnber being reduced to 4 in the gamete- 

 forming divisions (Fig. 03). Shellack and Leger, also, have described 



