144 



PROTOZOOLOGY 



into two parts. In the majority of the Mastigophora, the division is 

 longitudinal, as is shown by that of Menoidium incurvum (Fig. 67). 

 In certain dinoflagellates, such as Ceratium, Cochliodinium, etc., 

 the division plane is oblique, while in forms such as Oxyrrhis (Dunk- 

 erly; Hall), the fission is transverse. In Strehlomastix strix (Kofoid 

 and Swezy), Lophomonas striata (Kudo), Spirotrichomjmpha hispira 



Fig. 67. Nuclear and cytosomic division in Menoidium incurvum, 

 X about 1400 (Hall), a, resting stage; b, c, prophase; d, equatorial plate; 

 8, f, anaphase; g, telophase. 



(Cleveland), etc., the division takes place transversely but the polar- 

 ity of the posterior individual is reversed so that the posterior end 

 of the parent organism becomes the anterior end of the posterior 

 daughter individual. In the ciliate Bursaria, Lund (1917), observed 

 reversal of polarity in one of the daughter organisms at the time of 

 division of normal individuals and also in those which regenerated 

 after being cut into one-half the normal size. 



In the Ciliophora the division is as a rule transverse (Fig. 50), in 

 which the cytosome without any enlargement or elongation divides 

 by constriction through the middle so that the two daughter indivi- 

 duals are about half as large at the end of division. Both individuals 

 usually retain their polarity. 



Multiple division. In multiple division the body divides into a 

 number of daughter individuals, with or without residual cyto- 



