GROWTH AND DIVISION 



71 



A 



Fig. 15. Details of division in S. coerideus. 



A. Eight, four and two-fold splitting of granular bands to 

 produce the fine bands of the new frontal field enclosed by a 

 stage-2 primordium. The number of interpolated kinetics 



(clear stripes) is correspondingly increased. 



B. Macronuclear division according to Johnson, showing 

 clumping of nodes, followed by rod formation, pinching in two 

 of the nucleus by the dividing cell and beginning renodulation. 

 A preliminary constriction of the massed nucleus (c) may go to 

 completion {d') with larger portion extending into and contri- 

 buting to the nucleus of the proter. (After Johnson, 1893.) 



C. Persisting fission in late divider after posterior excision; 

 rod-form macronucleus distributes itself accordingly and is 

 unequally — but proportionately — divided. (After de Terra, 



I959-) 



