460 ALLIS. [Vou. XIV. 
fossa, near that external aperture, not only in man (No. 32), but 
also in certain, if not in all, animals in which it is found 
(No. 40). 
The external nasal aperture in the rabbit, cat, and man, is, 
_according to Hochstetter (Nos. 19, 20), the only primary open- 
ing of the nasal pit, the internal aperture being of secondary 
origin. The single external aperture of these vertebrates must, 
if this be true, be the homologue of the two apertures combined 
of. Amia. From Hochstetter’s descriptions I am, however, 
inclined to think that the nasal pit, in the animals investigated 
by him, simply closes irregularly by the partial coalescence of 
its lips at the distal end of the primary nasal depression, instead 
of at its middle point. The distal end of the nasal depres- 
sion, the future internal nasal aperture, is thus simply tempo- 
rarily closed, and then reopened after having been enclosed in 
the mouth cavity. Such being the case, the internal nasal 
aperture of man would be the homologue of the anterior 
aperture of Amia, the external aperture the homologue of the 
posterior aperture of Amia, and the lachrymal canal and 
pore a part of the suborbital lateral canal. Seydel’s statement 
(No. 40) that there is always, in the nasal sac of Amphibia, a 
line of non-sensory tissue extending along the floor of the nasal 
fossa, from the external to the internal apertures, strongly 
supports this supposition, the non-sensory line representing, 
naturally, the line where the lips of the primary nasal depres- 
sion have fused to form a canal. Further support of this is 
found in the development of Ceratodus. In this fish (No. 39, 
pp. 42-44) the nasal pit lies at first wholly outside the mouth 
cavity, as in Amia. A nasal groove is then formed, the ante- 
rior end of which is first enclosed, secondarily, in the mouth 
cavity ; and then the entire groove is so enclosed. The two. 
lips of the groove then approach and fuse, and the two nasal 
apertures are formed, exactly as in Amia. It is, moreover, to 
be noted that, although both apertures lie apparently inside 
the mouth cavity, in the adult, the anterior one of the two 
lies anterior to the upper edge of the mouth, as defined by 
Semon (No. 39, p. 45), —that is, in reality, outside the mouth, 
in the upper lip. This indicates that the nasal sac of higher 
