NASO-LABIAL GROOVE OF LUNGLESS SALAMANDERS. 13 



in early autumn along the banks of the brooks in which the larvae 

 live, have developed, with the assumption of terrestrial habits, these 

 distinctively adult characteristics, namely, naso-labial grooves 

 and well developed glands opening in connection with them. 



There exist, however, even in the larvae, certain indications 

 that the process of formation of a naso-labial groove has begun. 

 There is a ventral elongation of the external naris, which really 

 forms a very short groove (Fig. 8, gr.}. Ventral to this there 

 may be seen by following the horizontal sections for a short dis- 

 tance a slight incurving of the epidermis with a tendency here and 

 there toward the proliferation of cells (/r) of the lower of the 

 two layers, a suggestion, at least, of the beginnings of future 



PS 



-pgc 

 \ b 



FIG. 9. Detail of a horizontal section through the head of a Desmognathus fu&ca 

 larva ventral to the external naris, showing an early stage in the formation of the 

 naso-labial groove, X 2 37-5- PSi pigment within the cells of the epidermis; pgc, 

 pigment cells below and between the cells of the epidermis. Both forms of pigment 

 are absent from the region in which the groove is developing (gr) pr, proliferation of 

 cells from the under side of the epidermis, probably the anlage of a gland. Other 

 designations as in previous figures. 



glands. Noticeable is the absence of pigment in this region both 

 in the case of the epidermal cells and the connective tissue be- 

 neath the epidermis. The first glands to appear, and at this stage 

 the only ones present, are the two connected with the naris. 

 These are very short, the dorsal extends posteriorly through 

 three or four io// sections, the ventral one extends mesially and 

 is very probably the branch which later finds its way into the 

 intermaxillary space. 



The small adults, 33 to 45 mm., have the groove well devel- 

 oped. The number of glands connected with it seems to increase 



