1911 | Chandler: A Lymphoid Structure in Lepisosteus 93 
found in these areas. It is further significant that the substance 
stains exactly the same as the granules, red with eosin, and 
yellow with picro-fuchsin. I cannot say that the granules do 
pass into the vessels and disintegrate, but there is no positive 
evidence against it, and there are some facts in favor of it. 
Although the granules appear to be normal, the possibility exists 
that they may be due to parasitism, or some other abnormality. 
The masses of granules, from ten to twelve microns in diam- 
eter, are held together by some membrane, probably a very thin 
cell wall, but it is not evident in the sections. The granules are 
sometimes scattered somewhat when the mass is eut across just 
as are the melanin granules in the pigment cells. Associated 
with each mass there is a fairly large nucleus which shows much 
more plainly in some eases than in others (pl. 11, fig. 2). Due 
to the lighter coloring of the granules with picro-fuchsin, the 
nuclei show best with that stain. These granular masses are 
found in varying density throughout the gland, except in the 
open connective tissue network immediately behind and around 
the cerebellum. In the main body of the gland they are seat- 
tered in approximately the density shown in plate 11, figure 2, 
though possibly on an average shghtly more numerous. In the 
ear-like projections, however, they are far more dense, so dense, 
in fact, as to obscure all the other kinds of cells, and to conceal 
the reticular network entirely. 
DEVELOPMENT 
Thinking that the origin and development of this gland-lke 
structure might throw some more definite light on its nature and 
funetion, I sectioned a series of embryos ranging from 6 mim. 
to 22 mm. in length. The heads of these embryos were stained 
in toto in Delafield’s haemotoxylin, imbedded in paraffin, and 
cut in sections 10 microns in thickness. 
As the eosin counter-stain was the most effective with the 
adult, this was likewise used for the embryos. 
Up to the 18 mm. stage there could be found no indication 
whatever of any structure lying over the myelencephalon, the 
ependymal lining of the brain cavity coming in close juxtapo- 
sition to the cartilaginous roof of the skull, or lying immediately 
