REPRODUCTION 



213 



the calyx in which it normally lies, and moves with the spindle to 

 the posterior end of the cell. The spindle takes a position at right 

 angles to the long axis of the cell; chromosomes, probably eight in 

 number, are formed and divided, and two daughter nuclei result, 

 each of which is enclosed by a new calyx while new basal bodies and 

 blepharoplasts apparently arise from the polar centrioles (Fig. 

 98, B, C). Thus the old kinetic complex, with the exception of the 

 cytoplasmic centriole, is discarded and entirely new aggregates are 

 formed. 



Flagellates with shells or tests behave during division in different 

 ways. In the majority of cases division occurs within the test; 

 the daughter individuals leave the old test by way of the aperture 

 and form new tests; in other cases the tests as well as the cell bodies 

 divide, as in the Diniferida. As the apical and antapical poles are 

 different in the Dinoflagellida division is followed by regeneration 

 of the appropriate shell part that is missing. 



Fig. 99. — Vahlkampfia Umax. Nucleus in upper cell in full mitosis (promitosis). 



(From Calkins.) 



B. Division and Reorganization in the Sarcodina.— It is very 

 questionable whether any rhizopod divides in the very simple 

 manner described by F. E. Schultze for Amoeba polypodia. The 

 "limax" types indeed approach this simplicity (Fig. 99) but new 

 discoveries are constantly at hand to indicate that these are not as 

 simple as they have been described. Thus Arndt (1924) quite 

 recently has given creditable evidence of the existence in a simple 

 amoeba, Hartmannella (PseudocJilamys) kUtzkei, of a definite 

 centrosome with centriole which is permanently extranuclear 

 (Fig. 41, p. 85). x'Vt division of the cell the centrosome divides 

 and the daughter centers with their centrioles, take positions at 



