288 INEZ L. WHIPPLE. 



With regard to the relative importance of the lungs of sala- 

 manders as respiratory and as hydrostatic organs, it is a signifi- 

 cant fact that in no case have I found that a Diemyctylus or an 

 Amblystomct which was out of the water and using its lungs 

 normally in air-breathing, had sufficient air in the lungs to float 

 the body when it was dropped into water. Almost the first act 

 under these circumstances is to swim to the top and take in a 

 quantity of air sufficient to float the body. This indicates plainly 

 the secondary adaptation of the lungs as organs of buoyancy and 

 it is easy to see how in the case of a species like Diemyctylus 

 which has become thoroughly aquatic, the hydrostatic function 

 might become of so much greater importance than the respira- 

 tory as to account for the apparent degeneration of the lungs as 

 respiratory organs which is indicated by their simplicity of struc- 

 ture. Moreover, it is easy to understand how a mechanism such 

 as the ypsiloid apparatus for controlling relative buoyancy of the 

 anterior and posterior ends of the body, while useful to any lunged 

 form for the longer or shorter periods during which it normally 

 stays in the water, would become especially perfected in its action 

 in the case of a thoroughly aquatic species. 



D. Negative Evidence Furnished by Litngless Salamanders. 



In corroboration of the above conclusions as to the function of 

 the ypsiloid apparatus of lunged salamanders, we have the 

 negative evidence furnished by the habits of lungless forms in 

 which, with the single exception of Salamandrina perspicillata, 

 the Cartilago ypsiloides is apparently lacking. 



These forms have, of course, no hydrostatic poxvers. They 

 are thus, unlike the lunged salamanders, incapable of a comfort- 

 able, free-swimming existence at any depth, but owing to lack 

 of hydrostatic organs they must remain for the larger part of the 

 time at the bottom. As Camerano ('94, '96) has pointed out, 

 although certain lungless species may be more or less aquatic, 

 their activities, even when in the water, are terrestrial. Various 

 species of Spelerpes, PletJiedon and DcsinognatJins, for example, 

 will at first, when placed in an aquarium, swim to the surface, 

 then around and around the edge of the aquarium, as if seeking 

 a means of escape, but the instant that active swimming ceases, 



