NUCLBAK DIVISIONS IN AMOEBA 43 



spherical opaque amoebae vary greatly in size, the mothei 

 nucleus giving rise to only two daughter nuclei in the smaller 

 spheres. To facihtate description of this non-mitotic method 

 of division, I have used these smaller amoebae, and I have 

 drawn a series of stages with the karyosome (1) in elevation 

 (PL 2, tigs. 15-19) and (2) in plan (PI. 2, tigs. 25-31 and 34), 

 the product of the division being two daughter nuclei in 

 each case. 



The process is not a simple halving of the nucleus into two 

 hemispheres which then roll themselves up into discoid figures, 

 but seems to be as follows : a patch of chromatin blocks divide, 

 each block into two (PI. 2, figs. 10-13). This process gradually 

 extends to the whole of the chromatin. Simultaneously the 

 karyosome also divides into two, each daughter karyosome 

 assigning itself to one daughter set of chromatin blocks. The 

 outer set of daughter products sloughs off gradually from the 

 inner by the increase of nuclear sap and by the formation of 

 the necessary additional areas of nuclear membrane and two 

 daughter nuclei thus result. The distance between these 

 gradually increases. Very frequently the daughter nuclei in 

 one preparation show different views of the karyosome (PI. 2, 

 figs. 32, 33). Very complicated figures necessarily result during 

 such a process of division, a binocular eye-piece being essential 

 for the complete elucidation of the preparations in some cases ; 

 especially is this true when the mother nucleus is undergoing 

 rapid successive divisions into four or more nuclear products 

 (Ph 2, fig. 14). 



If a spherical individual in which the daughter nuclei have 

 not been separated be placed on a slide and made to assume the 

 expanded position, the nucleus is seen to resemble the ' folded ' 

 nucleus described by Schaeffer (4) as being characteristic of old 

 or large specimens of A . p r o t e u s . In the light of the above 

 interpretations of fission divisions these folded ' lobed ' nuclei 

 are due to the fact that some external physical condition has 

 interfered with the amoeba when division was in process, the 

 so-called ' lobed ' nuclei being incipient multinucleate struc- 

 tures. Now the amoebae are easily disturbed. They are 



