SURVEY OF STRUCTURE 43 



A careful search was made for the resorptive part of the swimbladder. No trace of an oval could be 

 seen or indeed of any such special capillary bearing region. 



Scopelengys tristis Alcock 

 I have confirmed Alcock's (1899) finding that this species has no swimbladder. 



Family Scopelosauridae 



In this family, which consists of several species belonging to a single genus, the swimbladder is 

 absent in adolescent and adult individuals. The larvae have not been examined. 



Suborder ALEPISAUROIDEA 

 Elsewhere I have stated that these iniomous fishes have no swimbladder (Marshall, 1955). 



Order MIRIPINNATI 



The swimbladders of these oceanic fishes have already been described (Bertelsen and Marshall, 1956). 

 During the larval phase the swimbladder is functional, but it regresses during the adolescent phase 

 and in Mirapinna, at least, is a rudimentary structure in the adult. 



. There are two retia mirabilia receiving blood-vessels that extend forwards from the posterior end 

 of the swimbladder. In a larval Parataeniophorus gulosus of standard length 27-5 mm. the front part 

 of the sac is thick-walled and the walls are invested with a well-developed gas-gland on either side. 

 The posterior part of the sac is thin-walled and is presumably concerned in the resorption of gases. 

 In an adolescent P. festivus of standard length 42-0 mm. the thin-walled part of the swimbladder 

 is much reduced and the retia mirabilia and gas-gland have begun to regress. In the rudimentary 

 organ of Mirapinna, these structures are barely recognizable. 



Order CETUNCULI 

 Family Cetomimidae 

 Ditropichthys stored (Goode & Bean) 

 St. 2059, 09 11-4' S., 05° 17-4' W., 30. iv. 37, N 450 B, 1900-1400 m. Standard length 30 mm. 



In this fish a small swimbladder was found with a strong attachment to the roof of the stomach. 

 The sac measured about 2-5 mm. in length. Entering the posterior end of the sac was an artery 

 coming from a vessel running along the stomach wall. Another vessel originating in the roof of the 

 body-cavity ran to the ' anterior ' end. 



Transverse sections through this organ revealed it to be much regressed, the small lumen having 

 a curiously complicated form. Much of the bulk of the swimbladder is formed by a voluminous 

 submucosa. The sections suggest that during the regression of the organ, the sac becomes doubled 

 back, the anterior and posterior ends coming together at the back. Within the lumen there were 

 remnants of the cells composing the gas-gland. 



The interpretation of this curiously regressed organ must be left until earlier stages in the life- 

 history become available. Evidently the larvae of this species have a well-formed gas-filled swim- 

 bladder. 



Cetostoma regani (Zugmayer) 

 No trace of a swimbladder was found in this species. 



woods 



HOLE, 

 MASS 



6-2 



