332 KOFOID AND SWEZY. 



division of the blepharoplast and the migration of the daughters 90° 

 to the poles of the intranuclear spindle we have a provision for the 

 division of the nucleus in some one longitudinal plane. The axostyle, 

 chromatic margin, and undulating membrane all split lengthwise, that 

 is in some longitudinal plane, and new parabasal or chromatic basal 

 rod grows out in such a morphological plane, as do also the flagella. 

 On purely morphological grounds the division of the organelles is thus 

 longitudinal. The fact that the activities of the extranuclear loco- 

 motor apparatus temporarily disarrange the earlier relations of these 

 organelles in the mobile and less organized cytoplasm of the late 

 mitotic phases does not in the least affect the plane of division of the 

 organelles in question. It remains longitudinal in spite of the possi- 

 bilities of varying locations of the zone of final constriction of the cyto- 

 plasm. 



This matter of the interpretation of the plane of division in Tricho- 

 monas is one of theoretical importance since longitudinal division is 

 regarded as a fundamental characteristic of the Euflagellata, as dis- 

 tinguishing them from the bacteria, especially the spirochaetes, and 

 from the Ciliata in which division is transverse, as well as from the 

 Dinoflagellata in which it is oblique. Exceptions to the universality 

 of the direction of the planes of division thus acquire added interest 

 and justly receive critical inspection. This seeming exception in the 

 trichomonads thus disappears when we base our interpretation on 

 morphological grounds. 



The Method of Division. 



The division is, as we have shown, truly mitotic though diverging 

 notably from metazoan mitosis in the complications due to the extra- 

 nuclear apparatus, the inclusion of the division center in the blepha- 

 roplast, the extranuclear position of the paradesmose, the homologue 

 of the central spindle, in the persistence of the nuclear membrane, in 

 the precocious splitting of the chromosomes, and in the absence of any 

 development of astral systems. On the other hand chromosomes split 

 lengthwise, migrate to poles of a spindle, share in the reconstruction 

 of daughter nuclei, and the extranuclear organization divides under 

 the leadership of an extranuclear division center, all after the general 

 manner of the metazoan mitosis. 



The interpretation of amitosis which Martin and Robertson (1911) 

 have placed on this process in trichomonads is clearly not applicable 



