The Lateral ISTasal Glands of Amphiuma, 159 



development continues, the groove becomes prolonged ventrallj by an 

 infolding of the epidermis, and other glands make their appearance 

 along its mesial border. In a large adult I have found as many as 

 twelve glands connected with a single naris and its groove. 



Comparing, now, these naso-labial glands of the Desmognathidae 

 and Plethodontidse and the external nasal glands of other salaman- 

 drids with the lateral nasal gland of Amphiuma, it is very evident 

 that we are dealing with homologous structures. This homology 

 is shown by the time of origin of the lateral gland during transition 

 from the larval to the adult form ; by the derivation of the gland from 

 the epithelium of the introductoi-y nasal passage ; by its close associa- 

 tion, not only in location but in time of origin, with the constrictor 

 and dilatator muscles ; and finally, by its first appearance, not as a 

 single gland, but as a group of several distinct tubules. In fact those 

 developmental changes which result in the final pseudo-alveolar nature 

 of the gland in Amphiuma are foreshadowed by the conditions shown 

 by many of the salamandrids. The chief difference in anatomical 

 relationships between the lateral gland of Amphiuma and the external 

 nasal glands of other forms is in the location of the glandular orifice 

 within the nasal passage rather than upon its margin. This differ- 

 ence is evidently due to the retention of the introductory nasal passage 

 by the adult Amphiuma, whereas in other forms it is a larval organ 

 and disappears in transition into the adult form. Thus the inner end 

 of the introductory nasal passage of Amphiuma is the real homologue 

 of the external naris of the Salamandrida, and the spiral fold which 

 closes the lumen at this point corresponds to the creseentic fold which 

 closes the external naris of other forms. 



We come now to the question of possible homologies among the 

 other Derotremata and the Perennibranchiata. The tubular glands 

 of Proteus, described by Oppel '89, offer some interesting points for 

 comparison with the external nasal glands of Salamandrida and the 

 lateral nasal gland of Amphiuma. Oppel apparently examined four 

 specimens of Proteus in regard to this point. The facts given in his 

 description of these four individuals I have tabulated as follows : 



