334 



THE PROTOZOA 



whole body of each sporont. The small clear cells produced stud 

 the opaque body of the sporont like pearls ; hence this stage is often 

 spoken of as the " pearl-stage " (perlage, etc.). The remainder of 

 the body of the sjforont is left over as residual protoplasm, which 

 may contain nuclei, but which takes no further direct share in the 

 development. The cells that are produced are known as the "primary 



^ 



*s 



- ; . r / v\x..\ 



Wi 



FIG. 147. Stages of nuclear division in the cyst of Pterocephalus (Nina) gracilis. 

 A, Resting nucleus with a centrosome at one pole ; B, division of the centro- 

 some ; 0, D, formation of the nuclear spindle and equatorial plate ; ejection 

 of the karyosome ; E, nuclear spindle, with the unpaired chromosome on the 

 left, also the remains of the karyosome ; F, diaster-stage, with the unpaired 

 chromosome stretching across, the karyosome on the left ; the centrosomes 

 have each divided again ; O, H, later stages of division ; /, J, K, reconstruction 

 of the daughter-nucleus ; the unpaired chromosome forms the karyosome. 

 After Leger and Duboscq (621); magnification of the figures, 1,200 diameters. 



sporo blasts," but a better name for them is the gametids, since each 

 one is destined to become a gamete. The amount of transforma- 

 tion which a gametid undergoes in becoming a gamete may be 

 very considerable, or it may be practically nil. In some cases the 

 male gamete develops a special structure, while the female remains 





