292 The American Naturalist. [March, 
nucleated red corpuscles multiply also by karyokinesis. When mature 
they are converted into the ordinary non-nucleated forms by the extru- 
sion of the nucleus. The extruded nuclei are dissolved in the blood 
plasma, and there is evidence to show that they take part in the forma- 
tion of fibrinogen. Owing to the loss of the nucleus the corpuscle 
assumes the biconcave form seen in circulating blood. 
The white corpuscles, or leucocytes, arise from the lymphocytes, 
which are formed in the lymphoid tissue, especially the lymphatic 
glands. The leucocytes enter the blood apparently as unchanged 
lymphocytes. Each possesses a single vesicular nucleus, surrounded by 
a small protoplasmic envelope, and has not the power of making amoe- 
boid movements. From this stage the cell develops by growth into a 
second stage, characterized by a large protoplasmic envelope and amee- 
boid movements. In the third stage the nucleus is drawn out into an 
elongated strap shape, and may become horseshoe shaped or coiled 
into a spiral. This cell is actively amoeboid, and by the fragmentation 
of its nucleus becomes converted into the multinucleated leucocyte 
of the blood. This latter is not, as was formerly thought, a cell in 
process of division, but rather a disintegrating form, the fragmenta- 
tion of the nucleus being the first step in the process. The author 
believes that the fragmented nuclei persist for a time as the blood 
plates. He is led to this conclusion both by an examination of the 
leucocytes when in the act of disintegrating, and by the similarity in - 
the appearance and manner of staining of the fragmented nuclei and 
the blood plates. The disintegrated leucocytes are dissolved in the 
plasma to form the paraglobulin, which is believed to be derived wholly 
from this source. 
The author discusses fully the work of others and his work has been 
already reviewed by Minot in the AMERICAN NATURALIST. In addition 
to the results of actual observation the paper contains a number of inter- 
esting suggestions. The most potent of these, perhaps, is the view as to 
how we may best attack the dark problems concerning the origin and 
relationship of the blood proteids, and the part which they play in the 
general metabolism.—E. Cooke. 
