SEA-FISHERIES LABORATORY. 267 



behind the second root and much ventral to it. Its 

 nucleus lies in the floor of the fourth ventricle very near 

 the middle line, and the root below joins the ventral 

 lateral line root proximal to its ganglion as in Meniclia. 

 After leaving the brain the motor root, which consists of 

 deeply staining heavily myelinated fibres, becomes so 

 confused with the anterior part of the auditory root that 

 their separation is difficult even with the microscope. The 

 auditory nerve, however, passes dorsally into the tuber- 

 culum acusticum, whilst the motor vii. enters the brain 

 below and immediately in front of it. The motor vii. 

 passes into the Truncus hyomandibularis. 



Of the four ganglia of the complex (g. v. -vii.) only 

 one remains distinct macroscopically. This is the 

 ganglion of the dorsal lateral line root, which in front is 

 situated just dorsal to the Gasserian ganglion, and behind 

 overlaps externally the root of the trigeminus. It is 

 entirely intracranial and is partly shown in the chart as 

 the cells at the base of the H. buccalis vii. The other 

 three ganglia are crowded between the brain and the skull 

 wall and apparently form one mass also entirely intra- 

 cranial except for the narrowed anterior extremity of the 

 Gasserian ganglion which extends outside the skull along 

 the H. ophthalmicus superficialis v. as far forward as sec- 

 tion 472 (cp. chart). When these three ganglia are 

 examined in serial sections it is seen that the most 

 anterior is the Gasserian ganglion. This overlaps exter- 

 nally the geniculate ganglion situated behind it, which in 

 its turn overlaps externally the ventral lateral line 

 ganglion — the most posterior of the three. Although the 

 three ganglia form a single very compact mass, it is not 

 difficult to define their boundaries, even where, as in the 

 case of the first two, the character of their cells is much 

 the same. In the ventral lateral line ganglion, the cells, 



