292 S. Vincent, 



the Sharks. As seen in section the alveoli appear more or less oval 

 in form, about 50 f.i thick and reaching 140 — 150 /-i in length. Each 

 is surrounded by a fibrous membrane about 2 i-i in thickness. The 

 cells are mostly elongated; some of the longest of these are 30 — 50 ^t 

 in length, and reach quite across the thickness of an alveolus. The 

 nuclei of the cells have an average diameter of 10 fi. The cell 

 protoplasm is coarsely granular and contains in a fresh state fatty 

 looking globules. The nuclei shevr nuclear figures in most cases. A 

 rich capillary plexus surrounds the alveoli, separating their connective- 

 tissue walls from those of neighbouring alveoli at nearly every point. 

 Here and there in the section these capillaries widen out so as to 

 constitute veritable sinuses. 



It may with advantage be noted here, before leaving the subject 

 of the Elasmobranchs, that the cortex of the suprarenal capsules is 

 not much altered in the ascending series from Pisces to Mammalia, 

 but that the medulla gradually undergoes a development, till from 

 cells which differ little from pigmented nerve-cells devoid of axis- 

 cylinder processes, arranged in irregular masses, we get the glandular 

 form of the Mammalian medulla. The specific secretion and chromogen 

 appear however even in Elasmobranchs. 



2. Ganoidei. 



The Sturgeon (Acipenser sfurio) is the only member of this 

 order about which I can make any positive statement. The suprarenal 

 bodies of this fish are yellow masses of varying size and shape, 

 scattered in the renal substance. I have nothing to add to the 

 description I have already given of the histology of these organs. 

 My former figure is reproduced (PI. XVII. fig. 10) and it will be well 

 to quote the description from my former paper [116]. 



"The rounded or elongated-oval alveoli (50 — 60 .« in diameter, 

 or even 100 f^i long by about 60 ^i broad) are bounded by bold thick 

 walls, averaging 3 /f in thickness (PI. XVII. fig. 10 al. w.) and the cell 

 outlines are admirably preserved. The preponderating shape of the 

 cells is round or oval, and in some parts they are seen to overlap, as 

 the section is thick enough to contain several layers (x). In other parts 



