INEZ L. WHIFFLE. 



from the facts already given as to the development of the ypsi- 

 loid apparatus in other Amblystoma larvae. Moreover, the lungs 

 are doubtless functional as hydrostatic organs and the ypsiloid 

 apparatus probably serves its usual purpose in controlling this 

 function. 



I have not had the opportunity to observe the habits of Cryp- 

 tobranchns. From the descriptions which have been given of its 

 habits, however, one can readily believe that its lungs and ypsi- 

 loid apparatus are important, functionally, as hydrostatic organs. 

 The large size of the ypsiloid cartilage and the well developed 

 state of its muscles is, in itself, an indication of its functional 

 value. Moreover, the body is relatively short and the three pos- 

 terior somites of the trunk, that is, the region .which would be 

 constricted by the action of the ypsiloid apparatus, form a suffi- 

 ciently large proportion of the entire length of the body to 

 render such constriction effective. 



With regard to the second group two general types of body 

 form may be observed - - the short, stout, heavy body of Nec- 

 tnrus, and the eel-like form such as Amphiuma and Siren. Cam- 

 erano ('96), has expressed his belief that in all these forms the 

 lungs have an important hydrostatic function. My own obser- 

 vations of the living animals have been confined to Necturus and 

 Amphiuma. The former I have never observed to float except 

 upon one or two occasions when the water has become very 

 foul. Under ordinary conditions the Nectnnis in captivity stays 

 at the bottom of the aquarium, often hiding in crevices between 

 rocks. Occasionally, especially if much disturbed, it will swirn 

 to the surface and take in air through the mouth by a gulping 

 motion. This is usually followed by an immediate escape of air 

 through mouth and gill-slits as the animal sinks slowly to the 

 bottom. Undoubtedly the natural habitat of Nectnnis is at the 

 bottom ; it has, therefore, no use for an apparatus controlling the 

 hydrostatic function of the lungs. Moreover the total lack of 

 all traces of an ypsiloid apparatus indicates at once that the 

 species has not descended from one with such an apparatus, 

 since the muscular vestiges in wholly lungless forms show how 

 very slowly the degeneration of such an apparatus occurs. 

 Neither can we believe that the Nectnnis is a permanent larval 



