GAS GLANDS OF SOME TELEOSTEAN FISHES. 247 



Trigla hirimdo (PI. V. fig. 43 j PI. VI. figs. 42, 44). 



Fig. 42 (X 1). Lateral "red bodies" (L.R.M.) as seen in ventral wall of bladder 

 (= lateral divisions of the elongated "red body," the median 

 divisions being hidden bj' the muscle-bands, M.B., in the middle). 

 G.E., the glandular epitlieliuni (too broad in figure). 



43 (X 16). Semi-diagrammatic transverse section through the middle of the 



"red body" represented in fig. 42. M.B., two strong muscle- 

 bands on each side of the middle linej KM., rete mirabile ; 

 L.R.M., lateral rete mirabile; G.E., glandular epithelium; 

 S., strand of nerve-fibres supplying muscles. 



44 (X 250). Glandular epithelium of bladder in transverse section. B.L., gland 



duct. 



Smarts oulgaris (PI. V. fig. 46 ; PI. VI. fig. 45). 



Fig. 45 (X 1). Appearance of "red body " in ventral wall of bladder. 



46 (X 16). Semi-diagrammatic transverse section across anterior end of "red 

 body." R.M., rete mirabile; G.E., gas gland epithelium; S.E., 

 general squamous epithelium lining bladder; B.L., bladder cavity. 



Smaris maurii (PL VI. fig. 47). 



Fig. 47 (X 250). Pseudo-massive epithelium of gas gland in transverse section. As 

 explained in the text, this type of epithelium is without doubt a 

 derivative from the folded type and so differs from truly massive 

 types of gas gland epithelia which are not secondarilyderived from 

 a folded condition. The perivascular spaces seen in the figure are, 

 in most cases at least, due to contraction. 



Ophidiam harbatum L. (PI. VI. figs. 48-50). 



Fig. 48 (X 1). Appearance of " red body " in ventral wall of bladder. 



49(X16). Semi-diagrammatic transverse section across "red bodJ^" S.E., 

 squamous epithelium; G.E., gas gland epithelium; R.M., rete 

 mirabile. Outer layers of the bladder wall stripped off. 

 50 (X 800). Large gas gland cells with intracellular ducts (IC.D.), which 

 possiblj^ represent the passages of bubbles to the exterior. B.L,, 

 bladder cavity ; INT.C.D., intercellular duct. 



So.v hoops (PI. VI. fig. 51 ; PI. VII. fig. 52). 



Fig. 51 ( X 1). Appearance of " red body " in ventral wall of bladder. 



52 (X cir. 27). Semi-diagrammatic transverse section through the middle of the 

 "red body" shown in preceding figure. R.M., rete mirabile; 

 S.E., squamous epithelium; G.E.. gas gland epithelium; B.Ii., 

 bladder cavity. 



Atlierina liepsetus (PI. VI. fig. 53; PL VII. figs. 54, 55). 



Fig. 53 (X 1). Appearance of "red body" in ventral wall of bladder (only the 

 vessels and retia mirabilia are seen). 



54 (X 1000). The glandular epithelium in transverse section. 



55 (X 1000). The glandular epithelium of a young Atlierina (15 mm. long) 



showing incipient division of the cells in a plane at right angles 

 to the bladder wall. C.T.C., connective tissue cells. Notice the 

 large size of the nuclei as compared with those in the adult gland 

 of another specimen. Though no capillaries are shown in the 

 figure, yet thej' are plentiful in most parts of the gland. 



Coris jtilis (PL VI. fig. 56 ; PL VII. figs. 57, 58). 



Fig. 56 (X 1). Appearance of " red body " in ventral wall of bladder. 



57 (X 16). Semi-diagrammatic transverse section of "red bodi'." Lettering as 



before. 



58 (X 500). The glandular epithelium in transverse section. B.L., bladder 



cavity ; S.E., superficial squamous layer of the glandular mass ; 

 BU., gas bubble; INT.C.D., narrow intercellular lumen. 



17* 



