198 ALBERT KUNTZ 



the entire ramus, as illustrated in the accompanying figure (fig. 9 

 A), contains numerous cells of nervous origin and presents the 

 appearance of an early migration path. In embryos 10 mm. in 

 length the tympanic nerve has been joined by fibers from the 

 geniculate ganglion. The lesser superficial petrosal nerve may now 

 be traced to a point a little below the level of the semilunar gan- 

 glion where a small mass of cells has become aggregated. In an 

 embryo 14 mm. in length (no. 511) this mass has become some- 

 what larger, but the cells are still loosely aggregated. In sagittal 

 sections of this embryo, as illustrated in figure 9 B, it is irregu- 

 larly^ triangular and its upper angle comes into very close prox- 

 imity with the semilunar ganglion. In sections of an embryo 13 

 mm. in length (no. 485), as illustrated microphotographically in 

 figure 22, there is apparent cellular continuity between the pri- 

 moridum of the otic ganglion and the semilunar ganglion. This 

 connection could not be observed in all embryos in approximately 

 the same phase of development. In embryos 14 mm. and over 

 in length the primordium of the otic ganglion lies in intimate 

 contact with the mandibular division of the trigeminal nerve. 

 This nerve, like the other divisions of the trigeminal, contains 

 numerous cells of cerebrospinal origin which apparently advance 

 distally along its course. Many of these cells are derived from 

 the semilunar ganglion, others probably advance from the rhom- 

 bencephalon along the motor root of the trigeminal nerve. 

 Even in relatively late stages, as illustrated in figure 30 which 

 is taken from a section of an embryo 14.5 mm. in length (no. 1267) 

 continuous rows of cells may be traced from the rhomben cephalic 

 wall into the motor root of the trigeminal nerve. Doubtless, 

 many of these cells advance peripherally along the motor fibers 

 of the mandibular nerve. Fibrous rami may now be traced from 

 the mandibular nerve into the otic ganglion. These rami, like 

 the rami of the maxillary nerve which enter the sphenopalatine 

 ganglion, are accompanied by migrant cells, some of which appar- 

 ently advance into the otic ganglion. This condition obtains 

 during a considerable interval. In embryos 20 and 21 mm. in 

 length (nos. 460 and 462), as illustrated in figures 10, 27 and 28, 

 the rami of the mandibular nerve leading into the otic ganglion 



