92 University of California Publications in Zoology 
The histological elements found in the connective tissue net- 
work of the gland, in addition to pigment cells, are of three 
kinds: (1) large, clear cells with small, deeply staining nuclei 
(pl. 11, fig. 2, eryth.) ; (2) large cells more or less deeply clouded 
with blue in material stained in haemotoxylin, and showing eyi- 
dence of reticular chromatin network (pl. 11, fig. 2, lewe.) ; and 
(3) cells filled with masses of granules staining deep red with 
eosin, and yellow with piero-fuchsin (pl. 11, fig. 2, gran. m.). 
The first cells above mentioned seem to be erythrocytes, as 
they have precisely the same appearance as those filling the 
vessels in the pia mater, where they are associated with fairly 
numerous leucocytes. They are scattered freely throughout the 
gland, entirely independent of vessels of any sort. This is very 
remarkable for an animal which has a closed blood system, and 
no explanation for such a phenomenon, if they really be erythro- 
cytes, has yet been found. These cells range from eight to ten 
microns in diameter, are clear and transparent, with small, 
round, deeply-staining nuclei, and are irregular in outline, 
though this may be due to slight shrinkage or contact with other 
cells. 
The second cells above deseribed have much the appearance 
of large leucocytes. They are very uniformly round in outline, 
and vary from seven to nine microns in diameter. 
The most peculiar and characteristic element present. how- 
ever, are the numerous cells filled with granules. The granules 
are about one and a half microns in diameter, and are very 
nearly the same in size as the melanin granules in the pigment 
cells. Where a pigment cell and a mass of granules have been 
cut in close proximity and both types of granules slightly seat- 
tered, it is difficult to distinguish them except by eolor. As 
stated above, they stain a very deep red with eosin, suggesting 
eosinophile granules in leucocytes, but they are larger and oeeupy 
the cell more completely, as figured by Rawitz (1900). With 
picro-fuchsin, on the other hand, they stain a deep yellow, similar 
to the color given to muscle fibres. In many of the vessels of the 
gland, especially in the larger ones, there are areas filled with a 
substance which strongly suggests granules in process of disin- 
tegration, and occasional seattered granules still intact may be 
