SEA-FISHERIES LABORATORY. 273 



indicated by a spot in the chart, the second branch arises. 

 This is the R. buccalis. It at once splits into a dorsal and 

 a ventral division. The former itself divides as it passes 

 through the skull wall above the trigemino-facial foramen 

 into a posterior R. oticns and an anterior R. buccalis 

 externus. The latter is the R. bnccalis internus, and 

 leaves the cranial cavity by the trigemino-facial foramen. 



2. R. oticus (r. ot.). — Passes almost straight upwards 

 and splits into two, one passing straight forwards and the 

 other, except for the curious bend at its termination, 

 straight backwards. The former supplies sense organ 13 

 of the infraorbital canal, the latter, after being reinforced 

 as above described, sense organs 14 and 15 (the last two). 



3. R. buccalis externus (out. hue). — Passes down- 

 wards and forwards, gives off a twig to sense organ 12 of 

 the infraorbital canal, and then courses as shown in the 

 chart to supply sense organs 7 to 11 of the same canal. 

 The first 7 sense organs of this canal were not enclosed at 

 the stage at which the sections were cut, and were hence 

 lying freely on the surface. The first three are supplied 

 by the R. buccalis internus, but no nerves could be traced 

 to the fourth, fifth and sixth sense organs. This is due to 

 the fact that the outer buccal nerve, after supplying sense 

 organ 7, becomes extremely thin, and as it coursed among 

 the numerous pigment cells on this, the ocular, side, could 

 not be traced. It is most probable, however, that it sup- 

 plied sense organs 4, 5 and 6. Comparison with the 

 eyeless side, where there is no pigment, does not help, as 

 the canal is shorter and develops more quickly. 



4. R. buccalis internus (in. hue). — Leaves the skull 

 cavity by the trigemino-facial foramen and accompanies 

 the superior maxillary nerve. In front, opposite the 

 infraorbital canal it divides into an upper inner buccal 

 (up. in. hue.) and a lower inner buccal {low. in. hue). The 



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