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Nachdruck verboten. 



The Morphology of the Swim-bladder in Teleosts. 



(Preliminary statement.) 



By Henry C. Tracy, Ph.D., Northwestern University Medical School, 



Chicago, U. S. A. 



With 10 Figures. 



(Schluß.) 



The comparative anatomy and morphology of the oval have never 

 been investigated. Our knowledge of the structure is limited to de- 

 scriptions by various authors who have studied it in a few isolated 

 species. It was vaguely mentioned by a few of the older writers, but 

 for the first adequate description of the oval we are indebted to 

 Corning ('88) who carefully investigated the histology of the swim- 

 bladder in Perca fluviatilis, Lota vulgaris, and Acerina cernua. Jaeger 

 ('03) described the oval in Sciaena aquila and Lucioperca sandra; he 

 was the first to recognise that the oval is the apparatus for removing 

 gas from the swim-bladder and therefore physiologically analogous to 

 the pneumatic duct in the Physostomi. Reis and Nusbaum ('06) have 

 discovered certain remarkable specialized modifications of the oval in 

 some species of the Ophididae. 



The epithelium develops a red gland similar to that found in the 

 preceding type, except that in many species the folding has become 

 very highly developed and complicated (c. f., the complex type of red 

 gland described by Coggi, '87). The morphology of the red gland in 

 its most highly developed forms has in the past been the subject of 

 some controversy but the comparative anatomy of the structure, as 

 well as what little has been ascertained of its development, unmistak- 

 ably indicates that, in its origin at least, it consists essentially of a 

 folding of the enlarged cells of the epithelial lining, which in many 

 species has become so complicated and secondarily modified that its 

 essential structure in the adult is not always evident. 



The swim-bladder with an oval is present in a very large number 

 of the Physoclisti. It will probably be found to be the predominant 

 type in the higher Teleosts, particularly in those species which lead an 

 actively pelagic existence. 



