MITOSIS AND CELL DIVISION IN EUGLENA 

 SPIROGYRA EHRENBERG. 1 



H. L. RATCLIFFE. 



I. INTRODUCTION. 



Cell division of the free-living flagellates has been studied with 

 special reference to (i) the presence of a centriole or division 

 center, (2) chromosome formation and division, and (3) the 

 origin of the motor organelles following division. 



Berliner (1909), Hartmann and Chagas (1910), Belaf (1916) 

 and others have described centrioles in the mitotic process of 

 several of the euglenoid flagellates. Tschenzoff (1916), Hall 

 (1923), Baker (1926) and others have studied this process in 

 others of the same group, but have found nothing which appears 

 to be a centriole. 



Chromosome formation in the prophase of mitosis has been 

 found to vary in different members of this group of organisms. 

 Tschenzoff (1916) found masses of chromatin forming about the 

 periphery of the nucleus in the prophase which eventually formed 

 chromosomes in Euglena viridis. In Menoidiwn incurvuin, Hall 

 (1923) found that the chromatin was organized in " thread-like 

 structures " which shortened and thickened to form distinct 

 chromosomes at this stage of division. In Euglena agilis, Baker 

 (1926) described the chromatin granules, which, in the vegetative 

 stage, lie on " nodes of a linin network," as fusing during the pro- 

 phase to form the chromosomes. 



Chromosome division in the metaphase of mitosis has been de- 

 scribed differently by various authors. Two types have been re- 

 ported transverse fission by Hartmann and Chagas (1910), 

 Belar (1916) and others, and longitudinal fission by Tschenzoff 

 (1916), Hall (1923), Baker (1926) and others. 



The origin of flagella following division has also been found to 

 vary in different forms. Hartmann and Chagas (1910) and Hall 



1 From the Department of Medical Zoology, School of Hygiene and 

 Public Health, Johns Hopkins University. This work was begun in the 

 Protozoology Laboratory, at Emory University, Atlanta, Georgia. 



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