REPRODUCTION 



149 



anser (Fig. 310, c), "each granule divides where it happens to be 

 and with the majority of granules both halves remain in one daugh- 

 ter cell after division" (Calkins). Hayes noticed a similar division, 

 but at the time of simultaneous division prior to cell division, each 

 macronucleus becomes elongated and breaks into several small 

 nuclei. 





Fig. 55. Macronuclear reorganization prior to division in Aspidisca 

 lynceus, X1400 (Summers), a, resting nucleus; b-i, successive stages in 

 reorganization process; j, a daughter macronucleus shortly after division. 



The extrusion of a certain portion of the macronuclear material 

 during division has been observed in a number of species. In Urolep- 

 tus halseyi, Calkins actually noticed each of the eight macronuclei 

 is "purified" by discarding a reorganization band and an "x-body" 

 into the cytoplasm before fusing into a single macronucleus which 

 then divides into two nuclei. In the more or less rounded macro- 

 nucleus that is commonly found in many ciliates, no reorganization 

 band has been recognized. A number of observers have however noted 



