PROTOZOA 



29 



division of the cytoplasm without relation to that of the nuclei, is 

 known as plasmotomy. It is usually binary, but occasionally takes 

 place by budding or is multiple. The plane of simple binary or of 

 repeated fission is often transverse to the principal axis — if there be 

 one — of the body, but in most flagellates it is longitudinal. Repeated 

 longitudinal fission in which the daughter individuals remain in 

 position is called radial; such fission is common in the green flagellates 

 of the order Volvocina (e.g. some species of Chlamydomonas, Fig. 23 



Fig. 23. Chlamydomonas. A, C angidosa, x 1000. B-D, the same, in fission 

 (radial). E-H, C. /ow^wi/g'wa in fission (pseudotrans verse). Highly magnified. 

 After Dill, with modifications, c.vac. contractile vacuole; cph. chromato- 

 phore; cu. cuticle; e. eye-spot; nu. nucleus ; /)_yr. pyrenoid. 



A-D). Sometimes an individual in longitudinal fission shifts in its 

 cuticle during the process, till the plane of division becomes transverse. 

 Fission of this kind is said to be pseudotransverse : it is seen, for in- 

 stance, in some Chlamydomonas (Fig. 23 E-H). In Polytoma (Fig. 24) 

 the only vestige of longitudinal fission consists in a slight obliquity of 

 the first division of the nucleus. 



Each type of fission takes place in some cases in a cyst and in others 

 without encystment. 



BRARY 



MASS. 



