1922] Swezy: Mitosk^ in Endamoeha Coll 323 



coU. The prophase of the two amoebae seems also to be similar, as 

 their figure III-c differs from the same stage in End-cimoeha coli only 

 in the lack of characteristic chromatoidal bodies. 



The abundance of chromatoidal substances present in the early 

 prophase of Eiidamorha coli obscures much of the development in 

 that period, the individuals from which the present studies were made 

 being especially rich in that substance. The lack of this substance in 

 Endanioeba legeri makes that species a more favorable object for 

 study of these early stages. 



The polar masses or centrosomes in E ndamoeba coli are rather 

 large (spread out) and often diffuse (pi. 29, fig. 8, 9), or may be 

 small (pi. 30, fig. 13). In the telophase they are incorporated with 

 the chromosomes (pi. 30, figs. 15, 16) but their further history could 

 not be traced with certainty. It is probable that the centrosome forms 

 the karj-osome in the new nucleus, while the chromatin of the chromo- 

 somes becomes wholly, or in large part, distributed over the liniu 

 reticulum and nuclear membrane. 



It is possible that a definitive centrosome may be present within 

 the larger structure which forms the polar mass, a suggestion of which 

 is found in the fact that this may be very small in some individuals. 



The iutradesmose is formed when the centrosome or karyosome 

 divides, and connects them until the final parting in the telophase. 

 The origin of this structure is shown with greater clearness in the 

 figures of Endavweha legeri by Mathis and Mereier (1917), referred 

 to above, and is called by them the centrodesmose. It is often difficult 

 to differentiate the iutradesmose from the spindle fibers, hence its 

 absence in some of our figures. 



The difJerenees to be found between the type of division described 

 above for Endamoeha coli and those described by other workers for the 

 various species of non-parasitic amoeba consist largely in the structure 

 of the spindle, centrosome, and iutradesmose and in the number and 

 size of the chromosomes. The differences, however, are more apparent 

 than real, as a closer examination will show. The residual mass of 

 chromatin derived from the karyosome and forming the polar caps 

 and central spindle (iutradesmose) is greater in amount in Nacgleria 

 gruberi (Wilson, 1916) and Amoeba tachypodia (Glaser, 1912), than 

 in Endamoeba coli or Eyidamoeba legeri, but the behavior of the 

 structures is essentially the same in both groups. The division of 

 Amoeba hyalina, as described by Hartmann and Chagas (1910), 

 repeats the same process in its essential details, although the amount 

 of chromatin involved in the centrosomes is here quite minute. 



