1020 The American Naturalist. [November, 
MORPHOLOGY OF THE BLOOD CORPUSCLES. 
BY CHARLES-SEDGWICK MINOT. 
T: one goes through the very extensive literature dealing with 
blood corpuscles one finds the most divergent views defended, 
and can hardly reach clear ideas, for the conceptions do not agree 
among themselves, either as to their structure or as to the devel- 
opment of the corpuscles. According to some the red corpuscles 
arise from the white; according to others the white corpuscles 
arise from the red; and according to still others both kinds arise 
from indifferent cells. In regard to one point only is the majority 
of investigators united, —namely, in the silent assumption that all 
blood corpuscles are of one and the same kind in spite of the 
absence of the nucleus in mammalian corpuscles. It is just 
this assumption that has caused endless confusion, and the mor- 
phology of the blood corpuscles can be cleared up only by starting 
with the recognition of the fundamental difference between nu- 
cleated and non-nucleated corpuscles. Farther, it must be recog- 
nized that no corpuscles, neither red nor white, arise from nuclei. 
The origin of red corpuscles from nuclei has been maintained 
several times. This notion is based upon defective observations. 
It is very easy in the chick, for example, to convince oneself that 
the first blood corpuscles are cells; in the area vasculosa, at the 
time of the blood formation, the red blood-cells are readily seen, 
in part lying singly, in part in groups (blood islands), adherent to 
the vascular walls; the free cells are constituted chiefly by the 
nucleus, which is surrounded by a very thin layer of. protoplasm, 
which is very easily overlooked, especially if the preparation is 
not suitably stained; this explains, I think, the statement made 
by Balfour (Works, Vol. I.) and others, that the blood corpuscles 
consist only of nuclei. By following the development along 
further we find that the protoplasm enlarges for several days, and 
that during the same time there is a progressive diminution in 
size of the nucleus, which, however, is completed before the layer 
