64 Reproduction and Life-Cycles 



chromosomes from the interphase chromatin. The nucleus moves into 

 the spindle, the nuclear membrane is said to disappear, and the chromo- 

 somes form an equatorial plate. Additional examples are found in Actino- 

 phrys (18), Pelomyxa (Fig. 2. 7), and Zelleriella (58). 



In paramitosis, condensation of the prophase chromosomes is less 

 marked and a typical equatorial plate is not developed. In Aggregata 

 eberthi (Fig. 2. 8, A-D), only one end of each chromosome extends into 



Fig. 2. 6. Mitosis in Diniorpha mutans; euniitotic type; basal portions of 

 flagella and a few axopodia are indicated at the poles of the division-figure; 

 x3135 (after Belaf). 



the equatorial zone of the spindle. Since the daughter chromosomes sep- 

 arate before they are shortened, later stages of mitosis suggest transverse 

 division of long chromosomes. Long chromosomes persist also in certain 

 Radiolarida (20), Dinoflagellida (29, 106), Euglenida (3, 115, 157), and in 

 Teratonympha (Fig. 2. 8, E, F). 



The picture presented during separation of the daughter chromosomes 

 depends upon the position of the centromeres and the length of the 

 chromosomes. Terminal centromeres (Fig. 2. 10, H), which have been 

 demonstrated in Holojnastigotoides (63), probably occur in Aggregata 



