218 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
the glossopharyngeus so much that they now lie opposite encephalomere 
VII. The two nerve Anlagen, however, usually remain connected with 
each other dorsally by a thin cellular strand. This strand is wanting 
in some cases, or may be present on one side of the embryo only. 
Dohrn (’90) has also stated that the separation of the seventh and ninth 
nerves is due to the crowding caused by the ear capsule, and he held 
that the connecting strand of cells was evidence of the original conti- 
nuity of the neural crest on the dorsal side of the ear. Behind the 
glossopharyngeus the neural crest extends in unbroken continuity into 
the trunk, but only its anterior portion, which forms the ganglionic 
Anlage of the Urvagus, extends ventrally between the mesoderm of the 
side plates and the superficial ectoderm into the region of the pharynx. 
In embryos with 38 or 39 somites (Plate 3, Fig. 15) the thalamic 
portion still extends as a compact cellular cord from the region of con- 
striction between forebrain and midbrain to a point above the eye, where 
it unites with the line of ectodermal cells which in later stages forms the 
ophthalmicus profundus trigemini. This nerve, because of its relations 
with the trigeminus, “primary trochlearis,” and “ thalamic ” nerves, is 
regarded by Marshall (’82) and Miss Platt (91) as a commissural nerve 
connecting the three nerves mentioned. It has also been regarded as an 
independent nerve (van Wijhe, ’82, M. Fürbringer, 97), and as a ramus 
dorsalis either of the trigeminus or the oculomotorius. The acustico- 
facialis Anlage, opposite encephalomere V, is still in continuity with that 
of the glossopharyngeus by means of a cellular cord dorsal to the audi- 
tory invagination, while the cells of the glossopharyngeus and vagus 
Anlagen no longer appear to be continuous dorsally, as they were in the 
previous stage. 
At a stage of development when the embryo possesses 42 to 44 somites 
(Plate 3, Fig. 16), and when two visceral clefts are formed, both the 
thalamic and trochlear portions of the trigeminus Anlage are much re- 
duced. In an embryo with 48 somites the thalamic portion consists of 
a strand or cord of cells which extends dorsally from the ophthalmicus 
profundus, at a point just above the eyestalk, toward the region of con- 
striction between primary forebrain and midbrain, where the two cel- 
lular strands coming from opposite sides of the head unite above the 
wall of the brain. Because of this union, Coggi (95) has considered 
this portion of the trigeminus Anlage as a connective “nerve,” uniting 
the lateral halves of the ophthalmicus profundus. Its position in Tor- 
pedo, according to Coggi, is anterior to the thalamencephalon. If 
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Coggi is correct, its position in Torpedo is clearly different from that 
