532 



BIOLOGY OF THE PROTOZOA 



instances but the phenomenon may be more widely spread than is 

 at present admitted. Two well authenticated cases are the coccidian 

 Aggregata eherthi and the gregarine IHplocijstis schneideri. Dobell 

 (1915) describes 6 chromosomes in the vegetative divisions of 



fifi 



A 



B 



A 



ff 



* 



dd' 



G 



%V^ 



c 





H 



E 



Fig. 222.— Chromosomes of Aggregata eherthi. Letters a to /, or a to /'designate 

 the haploid groups. A, prophase of the first division (male); B, nuclear plate of 

 same; C, anaphase groups at first division; E, chromosomes in macrogamete nucleus 

 before fertilization; F, chromosomes in zygote nucleus (diploid); G, paired chromo- 

 somes in nuclear plate of first zygote division; H, early anaphase groups of first zygote 

 division, and separation of homologous haploid groups. (After Dobell and Jameson.) 



Aggregata eherthi and Jameson (1915 and 1920) describes 3 in 

 Diplocystis schneideri (Figs. 222, 223). These numbers remain 

 constant in both organisms during gametogenesis, the mature 

 gametes have the same numbers while the diploid mnnbers 12 and 

 are present only in the zygotes (Figs. 222 and 223). With the 



