32 DISCOVERY REPORTS 



Umbra. The arterial supply for the network comes from the retial artery, while there is a vein running 

 forward and upwards from the chamber to the cardinal (?) vein. 



Examination of the Discovery fish revealed that Rauther's 'praevesica' is no more than a very 

 distorted oval. In this fish the oval lies immediately to the right of the retia mirabilia and the capillary 

 bearing surface is blown out in the form of a blister, due no doubt to the release of pressure as the 

 fish was hauled to the surface. Had sections been cut of this structure, it would also have looked like 

 an anterior chamber. At the base of the oval is a circular aperture with a diameter of about 0-75 mm. 

 which opens into the main cavity. From the rim of this opening radial muscles extend outwards and 

 are crossed by a complex of circular muscle fibres. Clearly the whole structure conforms to that of the 

 oval found in some fishes with a closed swimbladder, much like that described in the perch (Perca 

 fluviatilis) by Saupe (1939). 



Like Myctopham punctatum and Diaphus rafinesqnei, each of the other lantern fishes dissected has 

 an ellipsoidal swimbladder provided with three unipolar retia mirabilia. The gas-gland is three- 

 lobed, each lobe receiving a corresponding rete. An oval is also present. 1 In view of this, the de- 

 scriptions which follow will be confined to the more significant features. Immediately after the length 

 of the fish, measurements of the major and minor axes of the swimbladder appear in parenthesis. 



Electrona tenisoni (Norman) (Text-fig. i6d-f) 



St. 2023, 50 177' S., 00° 23-1' E., 28. iii. 37, N 100 B, 750-4oo(-o) m. B.M. Reg. no. 1948. 5. 14.16. Standard 

 length 47-0 mm. (4-5 x 1-5 mm.). 



The swimbladder of this fish is well developed, although this is hardly revealed by the dimensions 

 of the sac, which is much contracted. Three retia, almost 2-5 mm. in length, enter the anterior floor 

 to supply a heart-shaped gas-gland. The bunched-up appearance of the gland, which covers much 

 of the floor, also reveals the collapsed state of the organ. 



Towards the base of the retia, but more to the right side of the sac, is the oval, with wrinkled 



outer walls. The inner tissues lining the wall are folded and ridged, and bear a network of blood 



capillaries. The structure is almost closed, there being but a small opening (about 0-5 mm. in diameter) 



communicating with the main lumen of the swimbladder. The blood-supply consists of two branches 



from the retial artery and a large vein, which runs forward and upward to the cardinal vein between 



the kidneys. 



Electrona rissoi (Cocco) 



St. 101, 33 50' to 34°i3'S., i6°04' to i5°49'E., N 450, 40o-35o(-o) m. B.M. Reg. no. 1930.1.12. 597-8. 

 Standard length 61 mm. (12x4 mm.). 



This species has a capacious swimbladder occupying about three-quarters the length of the body- 

 cavity. On the right of the sac and just behind the anterior tip is the oval, which receives a large 

 vein and a number of small branches coming from the retial artery. The organ is almost closed, the 

 walls having a much folded appearance. Around the opening into the main cavity of the swimbladder 

 are circular and radial muscles. 



Electrona antarctica (Giinther) (Text-fig. i6a-c) 



St. 114, 52 25' 00" S., 9 50' 00" E., 12. xi. 26, N 450, 650-70o(-o) m. B.M. Reg. no. 1930.1.30. 622-7. Standard 



lengths of two fishes examined, 26-0 and 59-0 mm. 



St. 2535, 52 40-8' S., 02° 45-4' E., 16. i. 39, N 100 B, 1050-0 m. Standard length 36 mm. 



In all three fishes the swimbladder is oval in outline and is suspended in the body-cavity over the 

 forward half of the stomach. The sac of the smallest specimen measured a little more than 3 mm. in 



1 The part of the swimbladder serving for gas-resorption. 



