278 ROYAL SOCIETY OF CANADA 
cut in various directions. These ducts in Scyllium and Torpedo had a 
double epithelial layer, an internal consisting of small cells and an 
external of larger elements. Some of the latter had granules which 
stain deeply with fuchsin. 
Giannelli,t however, looked upon these structures in elasmobranchs 
as primitive islets. 
Oppel * pointed out masses of large cells in the neighbourhood of 
the canals, but did not come to any definite decision as to their exact 
relationship to the duct cells. 
Laguesse * has followed up and extended these observations, work- 
ing chiefly with Galeus canis. He considers that the solid masses of 
cells originally described by Oppel are derived from the external layer 
cf the small ducts. The “clear areas” are often large and. are consti- 
tuted not only by the ducts but aiso by small solid columns of cells, 
separated by connective tissue into small masses or even individual cells, 
generally without a membrana propria. These cells are finely vacuo- 
lated and are coloured red with fuchsin like those of the second variety 
of the external duct layer. Occasionally a lumen is continued into 
these masses of cells. : : 
Helly,* working with the embryo guinea-pig as well as the elasmo- 
branch fishes, confirms most of the developmental and morphological 
results of Laguesse. But, notwithstanding this, the author upholds the 
view that the islets are organs sui generis. He denies the existence of 
transitions between islet and zymogenous tissue either in the embryo 
or the adult. He does not pronounce definitely on the subject of an 
internal secretion of the islets. | 
We have examined the following species :— 
Scyllium canicula. 
Acanthias vulgaris. 
Mustelus laevis. 
Rhina squatina. 
Raja clavata. 
Raja circularis. 
We have been able to verify most of the observations of Diamare, 
Laguesse, and Helly, though, as will be seen, we differ materially from 
the first and last as to the interpretation to be put upon the appearances. 

'* Atti. d. R. Accad. dei Fisiocr. in Siena, Vol. xil, p. 106, 1900. 
? Lehrbuch der vergleich. mikr. Anat., Bd. iii, 1900; Ergebnisse der Anat. 
Bd. ix, Litt. 1899, Wiesbaden, 1900. 
5 C. R. de l’Association des Anatomistes, p. 14, Montpellier, 1902; Bibliogr. 
anat., t. x., p. 260, 1902. 
‘Arch. f. mikr. Anat., Bd. Ixvii, s. 124, 1905. 
