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•liieans of its gills as a fish, but when it burrows itself in the mud of these 

 tracts, which after the overflow of the river are left dry, then the swim bladder 

 and ductus pneumaticu^ come into play, and respiration is carried on mainly 

 through them. The swim bladder of the Lepidosiren is double, with many 

 cellular divisions, lung-like. The pneumatic duct is wide and short, and opens 

 out into the (Esophagus. It is kept open by a special provision ; there is, 

 moreover, a ptilmonary artery which conveys blood to the lung-like swim 

 bladder. So amphibian-like is the Lepidosiren in some respects that natuialists 

 differ whether they are to regard it as a Fish or a Batrachian. Owen is satisfied 

 that " the totality of the organisation of the Xf/)i(7osi>c» exemplifies its funda- 

 mental ichthycic nature." In the structure of the swim bladders of the Pohjpterus 

 and the Lepidosteus we meet with transitional states connecting the simplest 

 closed swim blaxlder with the double lung-like organ of the Lepidosiren ; and 

 this seems to be a verificaticwi of Mr. Darwin's remark on the swim bladder of 

 fishes when he says, "There seems to me to be no great difiiculty in beUeving 

 that natural selection has actually converted a swim bladder into a lung or 

 organ used exclusively for respiration." Mr. Houghton thought in Lepidosiren 

 we have a living witness of a Fish in a transition state towards becoming a 

 Batrachian. The embryology of the Lepidosiren would doubtless throw much 

 light on this question (applause). 



Had time i)ermitted there would have been a long discussion on this 

 interesting subject. 



