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brain, and the posterior portion of segment 4 the fibres of the oculo- 
motor nerves pass ventrally and laterally close to the ciliary ganglion 
and innervate the muscles of the eye. 
Fig. 21. Fig. 22. 
Fig. 21. Horizontal section through the right wall of the medulla of a Chick 
embryo with 14 somites, 33 hours old, The internal ridge just opposite the external 
groove (g) has at its apex a groove (g’). These grooves mark the dividing line between 
neural segments 7 and 8. XX 275 diameters. 
Fig. 22. Horizontal section through the left wall of the medulla of Salmo pur- 
puratus, 22 days old. Letters and figures the same as in Fig. 21. X 275 diameters. 
The fourth pair of nerves are connected with the dorsal and 
posterior region of the mid-brain or segment 5. 
The fibres of the anterior root of the trigeminus emerge laterally 
from the dorsal portion of segment 6 and pass caudad to the Gasserian 
ganglion. 
From segment 7 the main fibres of the trigeminal nerve pass 
cephalad to the Gasserian ganglion. 
Segment 8 has no nerve connection. 
Segment 9 is connected with the fibres of the seventh and eight 
pairs of nerves. 
Segment 11 is connected with the fibres of the ninth pair of 
cranial nerves. 
The discussion of the literature, already written, is reserved for 
the larger paper. 
