SUPRARENAL BODIES IN PISHES. 67 



.glandular arrangement into alveoli and its markedly granular protoplasm. The cell- 

 outlines, too, are clearly seen in the majority of instances (PI. XIII. fig. 43, al.w., ex.). 

 The alveoli appear to be arranged, in some parts at any rate, in a more or less radiating 

 manner round large veins or venous sinuses (PL XIII. fig. 43, v.s.). 



A very striking feature in most of my sections is the presence of structures which 

 remind one of the " demilunes " in mammalian mucous glands (PL XIII. fig. 43, d.c). 

 Their presence is quite clear and unmistakable, but I cannot guess at their significance 1 . 



The general appearance under the microscope reminds one very forcibly of cortical 

 suprarenal tissue in the Mammalia. The interior of the organ is made up of lobules 

 or alveoli, each enclosed in a delicate but distinct fibrous capsule about 2 ft in 

 thickness. These alveoli are of various sizes, more or less oblong in form, about 

 50 ^u thick and reaching 140-150 ,u in length, so far as I can judge by my sections; 

 in many cases fibrous tissue appears to divide the individual cells one from another. 

 The cells vary much in shape and size, the majority being elongated ; some of the 

 longest of these are 30-50 (x in length and reach quite across the thickness of an 

 alveolus. The nuclei of the cells have an average diameter of 10 ft. The above 

 description of the interrenal is taken from a specimen of Raja clavata. The interrenal 

 of Scyllium has much the same structure, but the alveoli are not perhaps quite so 

 clearly marked out. This applies to the Sharks generally. 



In CMmcera the anterior pair of the suprarenal bodies (" axillary hearts "), although 

 long preserved in spirit, presented appearances which are worth recording. It is 

 somewhat easier to imagine definite cells in the case of CMmcera than in the Elasmo- 

 branchs, for although there are no distinct cell-walls to be seen, yet the protoplasm 

 appears to be gathered in separate portions of varying shape round the nuclei. These 

 are of very different sizes and shapes. It is noticeable that there seems to be no 

 ganglion of any great size in immediate connection with the body, and undoubted 

 nerve-cells in its substance are almost totally absent. 



The interrenal of CMmcera shows on microscopic examination a distinct alveolar 

 arrangement as contrasted with the absence of such an arrangement in the paired 

 suprarenals. This corresponds with what is found in the Sharks and Rays. 



With regard to the true nature of these two kinds of body in Elasmobranchs, and 

 the question as to their relations to the suprarenal bodies in the higher Vertebrates, 

 there are one or two points to be noticed. 



1. The interrenal of the Cartilaginous Fishes bears a very striking external resemblance 

 to the structure which, in Amphibians and Reptiles, is always admitted to be a supra- 

 renal. Its colour, its position, and its proneness to become broken up at its anterior 

 end are all points of resemblance. 



1 The drawing (PL XIII. fig. 43) represents the appearances after hardening, double-staining in bulk, and 

 saturating with paraffin. When examined fresh, the structure is largely concealed by the abundance of fatty- 

 looking globules. 



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