SUPEAEENAL BODIES IN FISHES. 79 



VII. Summary and Conclusions. 

 A. Gross Anatomy. 



My investigations in this department have led me to conclude that : — 



1. Suprarenale are almost certainly present in all Elasmobranchii, Holocephala, 

 Ganoidei, and Teleostei, and very probably in Dipnoi also 1 . 



2. In Elasmobranchs the interrenal body is totally distinct and separate from the 

 segmental bodies, and there is no kind of connection between them. 



3. There is no " third kind of body " in relation to the kidneys, as Balfour surmised 

 there might be. 



4. The yellow bodies scattered in the Sturgeon's kidney are the true suprarenals in 

 Ganoids, and correspond to the interrenal of Elasmobranchs and the suprarenals of 

 Teleosts. 



B. Histology. 



The following points in histology are either new or have not been sufficiently 

 emphasized by previous observers : — 



1. In Elasmobranchs the interrenal body consists of definite alveoli, containing cells 

 tvith large nuclei, and curious structures resembling " demilune " cells of mucus-glands. 

 This structure indicates its " secretory " nature and its analogy to the suprarenals of 

 Teleosts and the cortical part of the suprarenals of the higher Vertebrates. 



2. The segmenially arranged bodies in Elasmobranchs have no cortex and medulla, no 

 definite alveoli, and cell-outlines seen only with difficulty. There are, however, in some 

 places branched pigment-cells which appear to communicate together by their processes. 

 The nuclei are of very varying size. 



3. These segmental bodies, having such a different structure from the interrenal, are 

 probably different also both morphologically and physiologically 2 . 



4. That the fibrils which Balfour observed in the substance of the paired bodies were 

 probably many of them only connective tissue, that the significance of the relations of 

 the faired suprarenals to the sympathetic has been much overstated, and that their 

 relation to the vascular system is probably much more important. 



5. The suprarenals in the Sturgeon have a structure which is definitely alveolar and 

 cellular — analogous to the interrenal of Elasmobranchs and the suprarenals of Teleosts. 



6. The interrenal of Elasmobranchs and the suprarenals of Ganoids and Teleosts are 

 in their essence ' ; secreting-glands" as the Mammalian organ is now believed to be. 



7. The segmental suprarenals of Elasmobranchs are also secreting-glands, though 

 probably of a different nature 2 . 



C. TIead-Kidney . 



1. That all Teleosts and Ganoids, as far as is known at present (except Lophius, 

 Dactylopterus, and Fierasfer, Orthagoriscus mola, Mora mediterranea, and all the 

 species of Macruridas), have a " lymphatic head-kidney ." 



1 See footnote 2, page 73. ■ See Anat. Anz. xiii. Bd. Nr. 1 & 2 (1897). 



