304 DR THOMAS H. BRYCE ON 
It measures 14 to 16 microms in diameter, and possesses a small halo of very delicate 
protoplasm, which varies in amount from a zone hardly to be made out except under a 
high power, to a well-defined envelope to the nucleus (fig. 23, Pl. III. ; fig. 44, Pl. V.). 
The protoplasm is nongranular, is hyaline in appearance, and even under a magnifica- 
tion of 1500 diameters it is not possible to make out more than the vaguest suggestion — 
of reticular formation. In methylene blue and eosin preparations it is very delicately 
stained by the basic dye, while in those tinted with Ehrlich’s ‘triacid’ mixture it has a 
faint grey tinge. 
I cannot with certainty demonstrate a centrosome. The nucleus is round, with a 
coarsish chromatin reticulum, loosely arranged. It colours violet with methylene blue 
and eosin, and no part of the nucleus is oxyphil, the linin taking a cold blue tint, while 
the karyosomes are deep violet. 
There is some doubt whether in all instances the nucleus is round, or whether there 
is a notching at one pole. I have observed some such nuclei, and it is obvious that the — 
notching could only be seen if the section passed through a plane at right angles to it, 
and through the centre of the body. 
(2) Large Mononuclear Hyaline Corpuscles. 
This variety occurs more frequently than the last, and is the commonest form seen 
in the blood stream. It measures 24 to 26 «in diameter. The protoplasm varies in 
amount, but is always merely a narrow zone surrounding the nucleus. 
In methylene blue and eosin preparations it has a very delicate blue tint, and 
high magnification reveals a very delicate meshwork, with microsomes at the nodal 
points, which stain brightly with the blue dye (Pl. III. fig. 24; Pl. V. fig. 45)55 
The nucleus is spherical ; the chromatin network is very loosely arranged, and therefore 
in a section (fig. 24) one sees only rounded bodies with delicate threads radiating 
from them. ‘These are not true nucleoli or plasmosomes, but karyosomes. So far as 
I can discover, plasmosomes do not occur in these embryonic nuclei. The staining 
reactions are interesting. In iron hematoxylin and eosin preparations the karyosomes 
are black and the general network red, but the chromatin parts more readily with the 
black stain than the chromatin of the red corpuscles, so that in sections which are suit- 
able for a study of the latter the white cells are almost purely red. In methylene blue 
and eosin preparations the karyosomes are deep violet and the network takes a blue 
shade, but, as in the small corpuscle, there are no purely oxyphil granules. The deep 
violet blue stands out in strong contrast to the delicate pure methylene blue staining 
of the protoplasm. 
In triacid material (fig. 25, Pl. III.) the network is green, and the karyosomes almost 
invariably retain some of the acid dye. The colour is sharply distinguished from the 
golden yellow of the chromatin of the red corpuscles, but also from that of the general 
mesenchyme nuclei, which stain pure green in preparations which show a yellow tinge 
in the leucocytes. In cells which show this staining, the chromosomes during division 
