199 EDWARD PHELPS ALLIS, JR. 
instead of being invaginated, this necessitating a secondary 
reopening of the occluded postero-lateral nasal aperture of 
Chimaera. The fact that the opening so formed is said (Hins- 
berg, ’01) to lie primarily in the dorsal wall of the anterior end 
of the alimentary canal, and hence posterior to the oral plate 
(bucco-pharyngeal membrane), can not affect this homology, for 
the choana of the adult still lies anterior to the bones developed 
in relation to the palatoquadrate, and hence quite certainly 
anterior and not posterior to the primary upper lip, between that 
lip and the secondary one. 
If this be the manner in which the nasal apertures of the 
Amphibia have been developed, and it seems to me that it must 
be, the embryological processes simply being obscured by con- 
densations and abbreviations, then the Amphibia must either 
be descended from some selachian similar to the one from which 
Chimaera is descended, or directly from some early Chimaeroid. 
The apparent similarity, in Chimaera and the Amphibia, in the 
relations of the buccalis latero-sensory line to the nasal apertures, 
is in favor of the latter assumption, and, furthermore, it seems 
improbable that these complicated and peculiar nasal apertures 
would have been twice developed in the vertebrate series. This 
origin of the Amphibia would also probably explain the palato- 
quadrate, the upper and lower labials, and the horny jaws of 
larvae of the Anura. 
From the preceding descriptions of embryos and adults, it 
is evident that the primary lips of all of the gnathostome verte- 
brates must lie primarily at or but slightly. anterior to the oral 
plate of embryos, for as the mandibular arches lie morphologically 
posterior to the plate, the cartilaginous bars of those arches must 
also have primarily had that position. It would then be natural 
to conclude that the primary upper lips, which lie immediately 
anterior to the teeth developed in relation to the cartilaginous 
mandibular bars, are developed from tissues which lie oral to 
the hypophysial invaginations, but that this is so in all verte- 
brates can not be definitely determined from the descriptions 
given of embryos. 
