170 



PROTOZOOLOGY 



as in Arcella, Pyxidicula, 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 

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

 longitudinal, as is shown by that of Rhabdomonas incurva (Fig. 69). 

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

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



b ^ 



ssfisSk 





Fig. 68. 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. 



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

 and Swezy, 1919), Lophomonas striata (Kudo, 1926b), Spirotricho- 

 nympha bispira (Cleveland, 1938), Holomastigotoides tusitala (Fig. 

 64) and others (Cleveland, 1947), and Strombidium clavellinae (Bud- 

 denbrock, 1922), 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. 



