GAS GLANDS OF SOME TELEOSTEAX FISHES. 



213 



bladder cavity (B.C.) in the median line of the ventral wall of the 

 bladder. In diagram G it is to be observed that the squamous 

 epithelium on each side of the glandular mass has become folded 

 (F.F.E.) and projects into the bladder cavity towards the median 

 line. In diagram F these folds have nearly met in the middle 

 line and lie dorsal to the gas gland in the bladder cavity ; also it 

 will be observed that on the left side the glandular mass itself has 

 become completely reflected towards the median line [F.L.G.G.), 

 anil lies in close apposition with the rest of the glandular mass. 

 Still more anteriorly, the two lateral folds of squamous epithelium 

 have, as shown in diagram E, united in the median line, so that 



Text-flir. 59. 



Diagrammatic transverse sections through the anterior end of fig. 67 (PI. VIII.), 

 where the rete mirabile supplies the epithelium of tlie gas gland. The diagram 

 is full}' explained in the text. 



two separate epithelia now lie in the bladder cavity above the gas 

 gland, the upper of which (I.F.E.) is continuous with the squamous 

 epithelium lining the rest of the bladder wall, and the lower 

 {O.F.E.) is continuous with the two sides (the left reflected as 

 just described) of the glandular mass, which latter therefore now 

 forms the thickened ventral wall of a tube. Diagram D shows 

 that the dorsal thin wall of the tube just mentioned is being 

 replaced by extensions of the glandvxlar mass, this replacement of 

 the thin epithelium being chiefly due to the increase in size of the 

 Proc. Zool. Soc— 1911, No. XY. 15 



