2 o DISCOVERY REPORTS 



the rete and then forks into two sub-branches (see Text-fig. 9B) serving the left and right halves of 

 the capillary area. Each sub-branch gives off arterioles dividing to form capillaries. The venous part 

 of the capillary circulation comes from the glandular veins from branches running along the inner 

 edges of the two lobes. These branches break up into venules and capillaries that join the arterial 

 complex. The capillary arterial stream is thus by-passed round the rete mirabile, but the return 

 venous flow eventually runs through this structure by way of the glandular veins. 



Text-fig. 9. Swimbladder of Argyropelecus aculeatus, viewed (a) in position in fish, (b) ventrally, and (c) laterally. Veins 

 shown black, arteries white, av, artery-vein association supplying gas-gland ; bpr, by-pass branch of retial artery ; en, resor- 

 bent capillary network; gg, gas-gland; ra, retial artery; rv, retial vein; rm, rete mirabile. (a, xi;b, x 22-5; C, x 17.) 



Argyropelecus olfersii (Cuvier) 

 Taken by M.V. 'Sarsia' off Concarneau. Standard length 38 mm. (4-5 x 3-0 mm.). 



The swimbladder is suspended in the upper half of the body cavity. The sac is oval in outline, and 

 as it is quite relaxed the walls are fairly thick. 



A long, club-shaped rete mirabile, with a length of 275 mm., enters the posterior end of the sac 

 to supply the gas-gland. An artery from the dorsal aorta and a vein from the cardinal system (between 

 the kidneys) run into the posterior end of the rete. 



The gas-gland extends over the roof, side walls and floor of the rear half of the sac, the part over 

 the first two regions appearing to be subdivided into five or six lobes. There is a single lobe on the 

 floor. Each lobe receives an artery and vein from the rete mirabile, while an interglandular capillary 

 network extending over the inner surface of the roof also obtains blood from anterior retial vessels. 

 Longitudinal sections also revealed that there is a capillary network in the floor of the sac (in front of 

 and around the gas-gland). A branch of the retial artery, which subdivides just before entering the 

 rete, runs under the latter and then forwards to break up into capillaries, which run over the inner 



