THE YPS1LO1D APPARATUS OF URODELES. 293 



form of a lunged salamander, since such a larval form would cer- 

 tainly show traces of an ypsiloid apparatus. In this connection 

 it may be noted that H. H. Wilder in a footnote to Miss Emer- 

 son's recent work on Typldomoge (1905) stated that Kingsbury's 

 (1905) suggestion that Nectums maybe a permanent larva of one 

 of the Plethoiiontidte is untenable, since all of the Pleth&dontidce 

 are lungless. It now seems that in view of its lack of ypsiloid 

 apparatus, Nectums is ruled out of all possible claim as a sala- 

 mander larva. 



My observations of Ainphiuma give evidence of greater hydro- 

 static powers than in the case of Nectums. While this animal, 

 like Nccturus, spends its time largely at the bottom of the aqua- 

 rium, burrowing if the mud. is sufficiently soft, it occasionally 

 comes to the surface of the water to breath air. To accomplish 

 this, the tip of the snout is thrust out of the water, the body 

 being sustained at the surface by its own active serpentine move- 

 ments. Air is taken into the lungs by the process of pulmonary 

 respiration already described for lunged salamanders. As the 

 air enters, the buoyancy of the body increases perceptibly, often 

 until the body actually floats. I have seldom, however, observed 

 a specimen to retain this buoyant condition for more than a few 

 minutes. It will swim down, allowing bubbles of air to escape as 

 it goes, until it rests with its usual stability upon the bottom. I 

 have sometimes observed, however, during these few minutes, 

 marked constrictions of anterior or posterior body regions with 

 corresponding changes of buoyancy of these regions, such changes 

 apparently aiding somewhat in directing the eel-like motion of 

 the animal. From my own somewhat limited observations I 

 should conclude, however, that the lungs of the Amphiuma sub- 

 serve mainly the respiratory function although there is a possi- 

 bility of use for hydrostatic purposes. In any case it is very 

 evident that an ypsiloid apparatus affecting as it does, only two 

 or three body somites, would be practically useless as an acces- 

 sory hydrostatic apparatus in the case of an animal with a long 

 eel-like body comprising a very large number of somites like that 

 of Amphiuma. This fact would in itself account for the lack of 

 such an apparatus in these slender, eel-like forms, Amphiuma3&& 

 Siren. The lack of all vestige of both ypsiloid cartilage and 



