REPRODUCTION 



143 



Cytosomic division 

 Binary fission. As in metazoan cells, the binary fission occurs very 

 widely among the Protozoa. It is a division of the body through 

 middle of the extended long axis into two nearly equal daughter 

 individuals (Fig. 51). In Amocha proteus, Chalkley and Daniel found 

 that there is a definite correlation between the stages of nuclear divi- 

 sion and external morphological changes (Fig. 66). During the pro- 



\j^':. 



b o\SS^ 









j(..-.^-. 





'^-'i5/^:f 



'^i^- 



r^d 



^\, ■ 



Fig. 66. External morphological changes during division of Amoeba 

 proteus, as viewed in life in reflected light, X about 20 (Chalkley and 

 Daniel), a, shortly before the formation of the division sphere; b, a later 

 stage; c, prior to elongation; d, further elongation; e, division almost 

 completed. 



phase, the organism is rounded, studded with fine pseudopodia and 

 exhibits under reflected light a clearly defined hyaline area near its 

 center (a), which disappears in the metaphase (6, c). During the 

 anaphase the pseudopodia rapidly become coarser; in the telophase 

 the elongation of body, cleft formation, and return to normal 

 pseudopodia, take place. 



In Testacea, one of the daughter individuals remains, as a rule, 

 within the old test, while the other moves into a newly formed one, 

 as in Arcella, Pj^xidicula, Euglypha, etc. According to Doflein, the 

 division plane coincides with the axis of body in Cochliopodium, 

 Pseudodifflugia, etc., and the delicate homogeneous test also divides 



