CRANIAL NERVES OF SIREN LACERTINA 305 
of the dorsal part of the medulla between the origins of the sev- 
enth and the ninth-tenth nerves it will be seen that the lateral 
line lobe (‘dorsal island’ of Kingsbury), into which the dorsal of 
the three lateral line rootlets of the facial nerve enters, has dis- 
appeared at the level of the origin of the [IX—X nerves. The two 
lateral line rootlets of the vagus nerve, therefore, enter that part of 
the brain wall (acusticum) that corresponds to the part entered 
by the two ventral of the lateral line rootlets of the seventh 
nerve. The lateral line component of the vagus nerve supplies 
all the lateral line fibers of the IX—X group, except those that may 
enter by way of the anastomosis between the dorsal lateral line 
facialis ganglion and the supratemporalis-auricularis X nerves. 
The lateral line rootlets, on combining into a flattened band at 
the side of the medulla, pass postero-ventrally into the vagus 
ganglion. 
The glossopharyngeal group of rootlets arises ventral and 
slightly posterior to the preceding, composed of a dorsal rootlet 
of communis fibers and a ventral motor rootlet. From their 
connections with the brain the lateral line and glossopharyngeal 
roots pass posteriorly parallel with, but distinct from each other 
until their respective ganglia are reached, except that a small 
band of fibers (fig. 14, Xrspt.) descends from the lateralis root and 
enters the extreme antero-dorsal part of the [Xth ganglion, 
later emerging from the vagus ganglion as the ramus supratem- 
poralis X. A few sensory fibers of a different character often, 
- perhaps always, descend with this small band of lateral line 
fibers. Their origin and occurrence is usually obscured by the 
dense medullation of the lateral line fibers. They appear to come 
from the communis portion of the third group of rootlets, at a 
point where the latter comes in contact with the lateral line root. 
They separate from the lateral line tract, as the latter passes 
out of the skull, and pass into the [Xth ganglion. 
The third group of rootlets (Xr.2) in Siren consists of two com- 
munis, two general cutaneous and a variable number of motor 
rootlets, the latter sometimes as many as ten in number. The 
motor rootlets evidently come from cells situated opposite or 
nearly opposite their point of exit from the brain. The com- 
