2 INEZ L. WHIPPLE. 



have I been able to find in any of the Derotremcs or the Peren- 

 nibranchs any trace of it. 



Moreover, since all of the species which are known to possess 

 the groove are lungless, and, since of those which do not possess 

 it only one, Sahiinandrina perspicillata, lacks functional lungs, it 

 is evident that the groove has some function associated with re- 

 spiratory habits and correlated with the absence of lungs. 



DESCRIPTION OF THE NASO-LABIAL GROOVE AND 

 ASSOCIATED STRUCTURES. 



In my study of the naso-labial groove and the organs asso- 

 ciated with it I have used mainly Desmognathus fnsca, the species 

 which I have been able to obtain in largest numbers, both in 

 the adult and larval stages. The following description applies, 

 therefore, particularly to this species. 



The methods of study employed have included much observa- 

 tion of the living animals under varied conditions, gross dissec- 

 tion, and the microscopic study of both horizontal and transverse 

 series of sections. Horizontal sections are particularly favorable 

 for the study of the groove, since in these it is cut transversely. 



FIG. I. Hiai of adult Disiujgitatbtts fusca showing external naris and naso- 

 labial groove, f, crescentic fold; gr, naso-labial groove; grl, labial (horizontal) 

 groove ; w/j and / 2 , orifices of first and second naso-labial glands. Other orifices 

 may be seen along the mesial side of the naso-labial groove and along the horizontal 

 groove. 



Externally the naso-labial groove (Fig. I, gr\ though a mere 

 line, may be easily seen even with the unaided eye, its conspicu- 



