The Lateral ISTasal Glands of Amphiunia. 161 



relatively short ones, it does not appear from the whole set of observa- 

 tions that the variation either in number or in length of tubules is in 

 any way proportionate to the size of the individual (cf. ISTos. 2 and 4). 



In the single specimen of Proteus examined hj me (a series of 

 transverse sections of an adult head, length of specimen unknown) 

 there are two tubules upon the right side and three upon the left. Of 

 the group of three the lateral is the shortest and measures 0.3008 

 mm. ; the medial one measures 1 mm., and the middle one of the 

 group 1.203 mm. There is, however, a disconnected tubule ending 

 blindly at both extremities, about 1 mm. long and beginning 2.106 

 mm. posterior to the blind end of the middle (longest) tubule, Assum- 

 ing that this detached portion was originally connected with the 

 longest tubule and tliat from some cause the intennediate region 

 has atrophied, the total length of this tubule would be 

 1.203 + 1.0 -f 2.106, or 4.309 mm. The two tul)ules on the right 

 side measure respectively 3.008 (medial), and 3.7r>9 (lateral). 



As to the orifices of the tubules my observations practically agree 

 with those of Oppel, who says "Diese ist fiir alle gemeinsam die 

 Stelle, an welcher die aussere l!^asenoffnung, d. h. der von einem 

 niedrigen Plattenepithei ausgekleidete Vorraum ausserhalb der mit 

 dem Riechepithel gekleideten ^ase an die aussere Tlaut angrenzt. 

 Von der hintern Seite dicser Oeffnung entspringend ziehen die 

 Canale zum Theil medial, zum Theil lateral unterhalb der im Bogen 

 nach hinten steigenden !Nasenhohle gieichfalls nach hinten, um, ohne 

 sich zu verzweigen, blind zu endigen." 



Oppel offers no theory as to the homology of these glands. He 

 assumes, however, that the longest tubule, which in one specimen 

 extends nearly to the eye, is the "Thranencanal," a conclusion which 

 has been overthrown ])y the later researches of Born '76. So far as 

 I know, the development of these tubules has never l)een studied, 

 but their general structure and location show that they are homo- 

 logous with the lateral gland tubules of Amphiunia and with the 

 external nasal glands of other amphibians. A point which would, 

 at first, seem important in the establishment of this homology is, 

 however, lacking in that, unlike the other forms in which external 

 nasal glands are present, there is no trace in Proteus of either con- 



