158 Inez Whipple Wilder. 



The latter author has not only described the glands themselves but 

 has shown that they have a definite association with the constrictor 

 and dilatator muscles of the external naris, since the ducts of the 

 glands pass through the loop of the former muscle. Moreover, he 

 emphasizes the importance of this anatomical relationship by showing 

 that in Triton and Amblystoma (the genera in which he investigated 

 the development of these organs) the muscles and glands arise 

 simultaneously, the former from the connective tissue in the walls 

 of the larval introductory nasal passage, the latter by evaginations of 

 its epithelial lining; and a similar mode of origin which he finds 

 in the Anura further establishes the general homology of these struc- 

 tures. 



In an article already referred to (Whipple '06) I have shown that 

 the external nasal glands of the Desmognathidse and Plethodontidse 

 belong to a series of tubular glands which I have collectively termed 

 the naso-labial glands ; some of these, the external nasal glands, have 

 their orifices near the margin of the naris, the remainder open along 

 the border of the naso-labial groove, a structure which is peculiar 

 to these lungless forms and extends from the latero-ventral angle of 

 the naris to the edge of the upper lip. Many of the naso-labial glands 

 are short, simple tubes ; a few, however, particularly those associated 

 with the naris itself, attain enormous proportions in their develop- 

 ment, often extending even posterior to the orbit. Moreover, they 

 become much complicated by the formation of branches and alveolar 

 convolutions. Their great extent and complexity has been shown 

 by Wiedersheim, but seems to have been overlooked by Bruner, who 

 describes the external nasal glands in general as exceeding but little 

 in extent the fenestra i-ostro-lateralis of the cartilaginous nasal cap- 

 sule. 



Ontogenetically the naso-labial glands of Desmognathus make their 

 first appearance in the larva as it approaches its transformation to the 

 adult stage, at the time when the only indication of a naso-labial 

 groove is a slight ventral prolongation of the external nasal orifice. 

 At this time two glands appear, the first an evagination of the epi- 

 thelium at the inner edge of the incipient groove, the second a lateral 

 evagination of the lining of the introductory nasal passage. As 



