134 JOHN BEARD. 
organ, and the olfactory nerve is a segmental nerve, the post- 
branchial and pre-branchial branches of which, in consequence 
of the absence of a nasal cleft, are not developed. In fact, the 
olfactory nerve is the sensory remnant of the most anterior 
segmental nerve. 
DEVELOPMENT OF THE Nose IN AMPHIBIA AND TELEOSTEI. 
Hoffmann has described the development in Salmo, but has 
not ascribed an epiblastic origin to the nerve; this, however, is 
the case in both Teleostei and Amphibians. In Amphibia 
Gotte held that the olfactory nerve was developed in meso- 
blast. In fig. 4 the developing olfactory nerve and organ of a 
Teleostean Rhodeus amarus is figured, and in fig. 3 a 
similar stage in Rana temporaria. In both cases there is 
an epiblastic thickening, with which is united the rudiment of 
a ganglion, and there is also the rudiment of a nerve, the 
future olfactory nerve (o/f. n.), just splitting off from the skin. 
The development here is precisely similar to the development 
of the fifth nerve in the frog as described by Spencer, or to 
that of the vagus in the same animal as described in the 
preceding pages. 
It is hardly necessary to say that these facts confirm what 
has been said of the nature of the nose in Elasmobranchii. 
NERVE OF THE SixtH SEGMENT—AUDITORY NERVE. 
In a former paper’ I suggested the homology of the auditory 
organ with the so-called organs of the lateral line or branchial 
sense organs. Subsequent investigation has only confirmed 
this suggestion. 
Gegenbaur originally ranked the auditory nerve as a dorsal 
branch of the seventh. On embryological grounds Marshall 
and Balfour had also been led to the conclusion that the 
auditory nerve was not in itself entitled to segmental rank, but 
was in its development only a dorsal sensory branch of the 
1 Beard, “On the Segmental Sense Organs, &c.,” ‘ Zool. Anzeig.,’ Nos, 
161, 162, 1884. 
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