202 ANNfr: porter. 



Longitudinal Division. 



The longitudinal division of the living organism has been 

 frequently watched. While the movements of the dividing 

 flagellates are noticeable, those of the smaller dividing pre- 

 flagellates are far less marked. 



When a flagellate is about to divide, the protoplasm of the 

 posterior end concentrates somewhat in the nuclear region, 

 and the organism appears to shorten. The protoplasm 

 migrates from the centre of the parasite towards the sides, so 

 that a comparatively clear area is left at the centre (PI. 12, 

 fig. 4(5). The greatest change at this stage is seen in the 

 blepharoplast and flagellum. The blepharoplast becomes 

 slightly dumb-bell-shaped (1*1. 12, figs. 44, 45) and gradually 

 constricts into two (PI. 12, fig. 46). The flagellum splits 

 rapidly at the body end (I'l. 12, fig. 46), and then, more slowly, 

 the halves become free. The nucleus meanwhile becomes 

 sliglitly indented in the median line (PI. 12, fig. 46) and then 

 gradually constricts into two, the halves migrating to the 

 periphery (PI. 12, fig. 47). During this nuclear division the 

 daughter-Hagella execute very vigorous lashing movements, 

 and a constriction appears at the flagellar end of the parent 

 organism. A split appears at this end (PI. 12, figs. 47-49), 

 and, at the same time, vacuoles in the clear median area fuse, 

 and thus the extension of the split is facilitated. The daughter- 

 organisms rapidly sepai'ate from one another, their appear- 

 ance at times being suggestive of diverging curved calipers 

 (PI. 12, figs. 51, 52). At length the two are practically in a 

 straight line (PI. 12, figs. 53-55), in which condition they 

 remain for a short time and then finally separate. 



The division of the pre-flagellate forms is initiated by the 

 division of the blepharoplast, and is followed by the division 

 of the nucleus and the appearance of vacuoles. A slight split 

 appears at one end (PI. 12, fig. 3), and the organism remains 

 in this condition until the flagellum of each half has partly 

 grown, when final separation is effected by their movements. 



Sometimes repeated division of a pre-flagellate form occurs 



