SURVEY OF STRUCTURE 31 



Continuing Rauther's description, the inner epithelial layer forms an extensive gas-gland covering 

 most of the floor and side walls of the swimbladder, and also the roof of the anterior part. There are 

 three retia mirabilia supplied by an artery that joins the dorsal aorta close to the coeliac artery, while 

 the venous return is through a vessel opening into the portal system. The left rete extends upwards 

 to the roofing part of the gas-gland, while the middle and right retia supply the remaining glandular 

 area. Measured from Rauther's fig. 13 the lengths of the retia, in the order just mentioned, are about 

 2-5-3-0 mm. 



Text-fig. 15. Swimbladder of Myctophum punctatum, seen (a) in position in body-cavity of fish, (b) laterally, (c) ventrally 

 (anterior part of organ). The oval of Diaphus rafinesquei is shown in Text-figs. 15 D and E. cm, circular muscle of oval; 

 ram, radial muscle of oval; gg, gas-gland; op, opening from oval into swimbladder chamber; ov, oval; ra, retial artery; 

 rv, retial vein ; rm, rete mirabile ; vov, vein to oval. Veins shown black, arteries white, (a, x 1 ; b, x 5 ; c, x 1 2 ; D, x 7 ; 



E, XI 5 .) 



There is an anterior chamber, called by Rauther the praevesica, opening into the right side of 

 the main sac just behind its forward tip. The chamber has an outer fibrous layer and an inner much- 

 folded layer of loose connective tissue containing a capillary network. Rauther remarked that this 

 hlood-system was like that he found in the respiratory part of the swimbladder of the mud-minnow, 



