280 ROYAL SOCIETY OF CANADA 
and frequently the protoplasm of the cells adjoining the lumen is more 
deeply stained than in those of the outer row. (See Fig. 1.) 
In addition to the ducts there are small solid columns of cells 
surrounded and separated from each other by delicate strands of con- 
nective tissue. These may frequently be seen to be continuous with 
the outer cells of the smaller ducts (see Fig. 2), which, however, is 
drawn from Mustelus laevis. 
Several ducts of varying sizes are often seen close together in more 
or less compact groups (Fig. 2). These, as pointed out by Laguesse, 
are in reality separate ductules, and not one and the same cut in various 
parts of its devious course, as was originally surmised by Diamare. 
It is not easy to verify the statement of Laguesse that the “ 
areas ” are endowed with a rich capillary supply, as is the case in the 
islets of higher animals. In many of our specimens, it is true, one 
can see a larger number of capillaries in the areas than in the zymo- 
genous tissue, but this we should naturally expect, on account of the 
larger amount of connective tissue in the neighbourhood of the ducts. 
In specimens fixed in corrosive sublimate and stained in the 
Ehrlich-Biondi mixture, the second variety of cell in the outer row of 
the ducts is shown red owing to the staining of very fine granules with 
the acid-fuchsin. In some cases there is no distinct difference in stain- 
ing reaction between the inner and outer rows of duct cells: In some 
of the cells of the smaller ducts a finely granular appearance can be 
detected. There are also occasional cells of a much larger size than 
the average. 
In Flemming and iron-hæmatoxvlin preparations the small ducts 
frequently appear of a general darker tint than the zymogenous tubules, 
ewing to the deep tint of the darkly staining cells above referred to 
in the outer, second, row. 
In some parts of the preparations the zymogenous cells are vacuo- 
lated and devoid of granules, while in other parts the latter are beau- 
tifully preserved. 
Mustelus laevis. 
clear 
In this species the appearance of the larger ducts resembles that 
of corresponding structures in Scyllinm canicula, except that the 
columnar cells are not uneven but present a regular circular outline to 
the lumen. 
The smaller ducts present two layers of cells and sometimes even 
traces of a third layer (see Fig. 2d). The cells of the internal layer 
are small, while the nuclei are comparatively large, so that there is very 
little cytoplasm visible (Fig. 2 d). This last is darkly stained with 
eosin. The nuclei of this row present a curious, crowded, over-lapping 
