REPRODUCTION 



235 



own periplast into a number of daughter individuals, which writhe 

 and twist over each other like a bunch of eels within the thin 

 envelope enclosing them (Fig. 122, 11). When this stage is reached, 

 the flagellum, which hitherto had been performing active movements 

 and causing the organism to rotate irregularly within the cell, 



u/Mdi^, i 





w 





imfm* 1 



Fig. 123. — Polystomellina crispa. A zygote (A) develops into an organism with a 

 microspherie type of shell (B) in which the nucleus divides by mitosis until many 

 nuclei are present which form chromidia. The protoplasm fragments into reproduc- 

 tive bodies or agametes, each having several granules of chromidia (C). Each agamete 

 develops into an adult with a macrospheric type of shell (D, E) : when adult these 

 fragment into hundreds of flagellated gametes (F) which fuse in fertilization and so 

 complete the cycle. (From Lang and Schaudinn.) 



disappears altogether, and the metabolic movements cease; the 

 body becomes almost perfectly spherical, and consists of the peri- 

 plast envelope within which a number of daughter trypanosomes 

 are wriggling very actively; the envelope becomes more and more 

 tense, and finally bursts with explosive suddenness, setting free 



