248 University of California Publications in Zoology [VOL. 19 



homologue of centriole, Binnenkorper and centrosome, and other char- 

 acters be excluded, then the classification may be all-inclusive. But 

 whenever other characters are correlated, exceptions or connecting 

 links become as common or more so than the rule, and only arbitrary 

 progress is made. 



Alexeieff 's ' ' Systematization de la mitose dite 'primitive,' " (1913) 

 into five types promitose, haplomitose, mesomitose, paramitose, and 

 panmitose each subdivided into two subtypes, is the best possible 

 illustration to what extremes one will be led who attempts to bring order 

 out of the chaos of protozoan mitoses. With this elaborate schedule, 

 there are many misfits and the exceptions become the rule or the logical 

 connecting links. Euglena (Tschenzoff, 1916) fits into none of the 

 categories. Collodictyon fails to conform to any of his categories, -the 

 centrosome being extranuclear and the nuclear membrane persistent. 

 Furthermore, the chromosomes form partly from the chromatin of the 

 microkarosome, partly it seems from the macrokaryosome and partly 

 from peripheral chromatin granules, just as in panmitose. Thus it, 

 too, is a conspicuous exception and emphasizes the arbitrariness of 

 such attempts at elaborate classification. 



Alexeieff (1913) attached little importance to the presence or 

 absence of an equatorial plate, as a basis for classifying mitoses. His 

 reasons assigned are very good and can be referred to by all interested. 

 He emphasized the "centriole theory" and distinguished three types 

 of mitotic figures as they possess (1) polar bodies, (2) centrioles, or 

 (3) neither polar bodies nor centrioles. He suggested that polar bodies, 

 reduced, might be homologous to centrioles, but then, with fine-spun 

 distinctions, claimed that such were only present in mesomitosis and 

 rheomitosis. What he regarded as the "pseudo-polar bodies" of 

 haplomitosis, not being siderophile, could not be homologized with 

 centrosomes by him; he, therefore, concluded that haplomitosis was 

 very primitive and ' ' particuliere. " Hartmann (1911), Nagler (1909), 

 and Chatton (1910) considered centrioles very general in Protozoan 

 nuclei; Dangeard (1901), Alexeieff (1913), and Glaser (1912) con- 

 sidered them very rare. 



Calkins (1903) suggested the constitution and role which chromatin 

 plays in division as a basis for classification of the types of mitosis. 

 Tschenzoff (1916) expressed the same suggestion, having failed to find 

 a division center in Euglena, except the nucleolo-centrosome, the 

 Binnenkorper not initiating cell division, but persisting much as a 

 nucleolus of metozoa. 



