SURVEY OF STRUCTURE 



33 



length and 3 mm. in greatest width. The retia mirabilia are contained in a conical projection at the 

 anterior end, and they are wound spirally round one another. When opened out, three long retia 

 were revealed, each about 5 mm. in length, these running to a gas-gland covering about three- 

 quarters of the swimbladder floor. 



st Iv sb 



B 



rm gg st 



Text-fig. 16. Swimbladders of Electrona antarctica (a, b and c) and E. tenisoni (d, e and f). b, c, e and F are ventral views. 

 gg' gas-gland; hit, intestine; k, kidney; h, liver; ov, oval; oy, ovary; ra, retial artery; rv, retial vein; rm, rete mirabile; 

 sb, swimbladder ; st, stomach ; vov, vein to oval, (a, x 3-5 ; b, x 15 ; c, x 17-5 ; d, x 6 ; E, x 18 ; F, x 14.) 



The fish from St. 2535 has a rather larger swimbladder measuring nearly 4 mm. in length. In this, 

 the arterial supply for the retia mirabilia came from the coeliaco-mesenteric vessel. The walls of the 

 bladder were quite thin. 



Finally, the swimbladder of the 59-mm. fish measured no more than 2-0 and V2 mm. across the 

 major and minor axes. It is clear that the organ regresses during the adult phase. 



