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TRE AMERICAN NATURALIST [Vol. LI 



appearance of passing througli the food vacuole, begin to 

 degenerate and eventually both disappear. The chromatic 

 line endures for a longer period, however, and remnants 

 of it maybe seen for some time after the "line of blocks," 

 axostyle and undulatory membrane have vanished. The 

 blepharoplast also can be detected as long as the remnants 

 of the chromatic line are visible (Figs. 6, 7). This in- 

 crease in the size of the food vacuole seems to be due, 

 partly at least, to the taking-in of fluid, since while this 

 process is occurring the flagellate is increasing in size and 

 becoming more plastic in the constitution of its proto- 

 plasm. 



The food vacuole has now increased in size to represent 

 the greater part of the flagellate cell and is surrounded by 

 a crescentic ring or layer of cytoplasm seemingly much 

 reduced in amount (Fig. 5). From this time on the most 

 important changes concern the nucleus. This is now flat- 

 tened or sometimes flask-shaped, and soon divides into 

 two equal portions which travel through the region of 

 .cytoplasm to take positions at opposite sides of the ball 

 of reserve substance (food vacuole). Here each experi- 

 ences a further division resulting in the production of 

 four daughter nuclei (Figs. 7, 8). These apparently may 

 divide again until either eight or sixteen daughter nuclei 

 are formed occupying positions about the periphery of 

 the cell. Frequently smaller portions of nuclear sub- 

 stance are to be seen in the cytoplasm following the first 

 nuclear division and it is probable that these represent 

 reduction bodies (Fig. 8), although the writer has not 

 observed them in the course of formation. About the 

 daughter nuclei there seems to gather by slow degrees a 

 layer of cytoplasm and eventually they break out of their 

 peripheral ring of maternal cytoplasm to enter the ball of 

 reserve substance occupying the center of the cell (Fig. 

 10). This is gradually consumed by the young organisms 

 which slowly take on an elongated shape. During this 

 time the cyst wall which had formed about the mother cell 

 has been weakening and finally the young organisms 

 break out of the mother cell and appear as the youngest 



