284 ROYAL SOCIETY OF CANADA 
forms between the zymogenous and the islet element (see Figs. 3, 4 i). 
The islets as also the zymogenous tubules are outlined by a very definite 
membrana propria (see Figs. 3 and 4). 
Raja clavata. 
In this species we have to rely only on material fixed in Flemming’s 
fluid. The light islets are not very obvious, though ductules are not 
infrequent in our sections, and these consist, as in other species of 
elasmobranch fishes, of several rows of cells. In some of the smaller 
ducts there are two rows of cells, the outer row consisting of larger 
elements than the inner. Some of the outer cells have a homogeneous 
steel-blue tint (iron-hæmatoxylin preparations). Still others are very 
deeply stained by this method; giving rise to an appearance very like 
that described in the case of Rhina squatina (q. v.). There are occa- 
sional islets of the same character as those described for Rhina, separate 
from the ducts but near them. These are well seen in safranin slides 
and show an abundant capillary supply. 
Raja circularis. 
Our material was fixed in corrosive sublimate. When the pre- 
parations are stained with hematoxylin and eosin we readily see ducts 
with two rows of cells, as in scyllium, but not so numerous. There 
are also some few separate islets consisting of cells of the same char- 
acter as those in the outer row of the ducts. These are usually in 
close proximity to the ducts, but may be at some distance from them. 
NOTE ON BATHYCHROME TISSUE. 
In our previous communications’ we described certain striking 
appearances, hitherto unnoticed, in the vertebrate pancreas, under the 
name of “bathychrome tissue,” represented in mammals for the most 
part by small groups of cells or even solitary elements scattered 
throughout the secreting alveoli. In birds, reptiles, and amphibians in 
addition to the “leptochrome” islets, or islets of Langerhans, there 
appear to be solid masses of cells of a different character. These stain 
very deeply with most ordinary staining reagents and are specially 
marked after fixing with Flemming’s fluid. ‘They constitute the 
“bathychrome ” tissue in these animals (see illustration to former 
paper*). In an appendix we expressed some doubt as to the signifi- 

3 Loc cit. 
2? Loc cit. 
