22 DISCOVERY REPORTS 



retial vessels formed a capillary network over the inner surface of the sac between the lobes of the 



gas-gland. 



Polyipnus laternatus Garman (Text-fig. ioa, b) 



Position, 13 25' N., 18° 22' W., 28. x. 25, N 450 V, 90o(-o) m. B.M. Reg. no. 1930.1.12. 458-67. Standard 

 lengths 32-5 and 26-5 mm. 



St. 1582, 05° 39-1' S., 46 22-3' E., 29. v. 35, N 450 H, I900-i85o(-o) m. Standard length 36-0 mm. 



The swimbladder of this species is suspended in the upper half of the body-cavity, just above the 

 stomach. The sac is more or less oval in side view, with its long axis parallel to that of the fish. In 

 the three individuals examined (in the order given above) the sac had a length and middle depth of 

 7-0 and 4 mm., 175 and i-o mm. and 6-o and 3-5 mm. 



Text-fig. 10. Swimbladders of Polyipnus laternatus (a and b) and Sternoptyx diaphana (c and d). a and C, lateral views, 

 showing position of swimbladder in body-cavity ; c and D, rete mirabile and gas-gland, ft, fatty investment of swimbladder ; 

 gg, gas-gland ; k, kidney ; oy, ovary ; rm, rete mirabile ; st, stomach, (a, x3-5;b, xii-5;c, x5;d, x7 - 5-) 



A long club-shaped rete mirabile enters the posterior end of the swimbladder, the measurements 

 of its length in the two largest fishes being about 3-5 mm. The gas-gland lies immediately in front of 

 the rete and is partly or entirely divided into two left and right halves. 



A layer of fatty tissue invests the swimbladder walls of the 26-5 and 32-5 mm. fishes. The de- 

 position of the fat takes place between the peritoneal layer surrounding the sac and the tunica externa, 

 transverse sections through the swimbladder of the 36 mm. fish revealing that the space between 

 these two layers is filled with loose reticular connective tissue (see also p. 67). The resorbent capillary 

 circulation has not been closely investigated. However, there is an artery running forward by the 



