MOVING PHOTOMICROGRAPHY— KAZEEFF 329 



podium of the amoeba is on the point of engulfing the extremity of 

 an oscillating alga. The pseudopodium progresses slowly about the 

 algal filament as shown in figure 2, taken 55 seconds later. It finally 

 withdraws, carrying with it the algal filament which penetrates a 

 small distance into its protoplasm (fig. 3, taken at 11:22). It is by 

 similar movements repeated many times that the amoeba absorbs 

 the entire filament. 



Certain amoebae are also nourished by the protoplasm of cells of 

 molds. In plate 6, figure I, there are shown two amoebae braced 

 against the same plant cell and attacking the cellulose membrane; 

 the time is 11:25. At 11:28, the amoeba on the right has pierced 

 the wall and absorbed the cell contents which pass into the amoeba 

 and form a large vacuole. At the same time, the other amoeba 

 detaches itself from the support and moves away (fig. 2). 



KARYOKINESIS 



The following pictures were taken of the red blood corpuscles in the 

 mother cells of the Triton, the diameter of which is about 0.025 

 millimeter. The nucleus, which is very large, occupies almost the 

 entire cell, and lilvc the cytoplasm of the rest of the cell, it is relatively 

 opaque. Plate 7, figure 1, taken at 7:36, shows a cell that is ready 

 to divide. The protoplasm is animated by very slow movements, 

 difficult to distinguish by direct examination, but clearly visible in 

 the projection because of the enlargement (about 50,000 times) and 

 the acceleration of the movements, the speed being multiplied, 

 according to the case, by 16, 48, 112, and even 480. 



At this early stage, there may be observed a rotation of the nucleus 

 in the plane of the preparation. This rotation may be, in one case, 

 360° in 6 minutes, in another case, about 225° in 23 minutes, in a third 

 case, about 180° in 27 minutes. Probably this rotation results from 

 the efforts of the nucleus to embed itself into the cytoplasm before 

 division. 



There then ensues the gradual formation of the nuclear spireme; 

 the disappearance of the nuclear membrane is very rapid (fi.g. 2 

 at 7:45). At this moment, the deformations at the periphery of the 

 cell cease abruptly. The spireme becomes loosened and forms 

 strands which are generally placed at the periphery of the cell and 

 in the plane of the preparation when the cell is Ughtly pressed with a 

 cover sUp. The transversal division of the threads of the spireme 

 gives rise to the chromosomes which begin to form the equatorial 

 plate (fig. 3 at 8:27). In those chromosomes situated in the focal 

 plane, the phases of the longitudinal division can be followed, then 

 the migration of the new elements toward the poles of the diaster 

 (fig. 4 at 8:35). The chromosomes then group to form two daughter 

 nuclei (fig. 5 at 8:42). At the moment of the constriction of the 



