BRAIN OF THE ' WHITE ANT' 575 



In sections (figs. 13, 21, 24) the frontal ganglion is rather tri- 

 angular in appearance, the apex composed of nerve cells and the 

 base of nerve fibers. The nerves connected with the frontal 

 ganglion are (1) the paired tritocerebral or labrofrontal nerves, 

 l.f.n., (2) the paired labral nerves, la.n., (3) an unpaired nerve to 

 the protocerebrum, (4) the unpaired recurrent nerve, r.n. 



The tritocerebral or labrofrontal nerves, l.f.n., arise from the 

 trjtocerebrum as described under that heading, and their anterior 

 ends are connected with the latero-ventral surfaces of the front.al 

 ganglion. 



From the median ventral surface of the frontal ganghon a 

 bundle of nerve fibers emerges that runs first ventralward for a 

 short distance and then divides into delicate right and left 

 branches that pass to right and left through some muscle fibers 

 in the clj^peus, continuing down and forward into the labrum as 

 two delicate but distinct nerves. Those branches are distributed 

 throughout the labrum. I have termed these nerves the labral 

 nerves. In this I am apparently not in agreement witli Holm- 

 gren ('09) who does not describe the labral nen'es as arising from 

 the frontal ganglion but speaks as tliough the labmm were inner- 

 vated directly from branches of the labrofrontal nerves, which 

 is not the case in L. flavipes. In all the sections which I have 

 examined the nerves of the labrum have no direct connection 

 with the labrofrontal nerves but arise indirectly, from the base 

 of the frontal ganglion as described above. To quote Holmgren : 



Ganglion frontale liogt iinmittelbar vor dem obcren Schlundganglion 

 und ist mit diescin durch einen iinpaaren Nervenfaser, dcr iin Proto- 

 cerebrum eintritt, verbunden, Vor dcm Ganglion frontale gehen nach 

 vorn Nerven aus, welche einige clypealen Muskcln innervicren. . 



An den Seiten des Ganglion frontale konimen die tritocercbralen Kon- 

 nective ein, und hintcn lauft der ncrvus re^urrens aus, um oberhalb des 

 Darmes sich nach hinten zu begeben. 



Aus TritocGrebruni werden folgende Teile inn6rviert: 



1) Die ganze oben beschriebene Labralmuskulatur von n. labro- 

 frontalis 



2) Die Labraldriisen von n. labrofrontalis. 



In agreement with Holmgren I find a verj^ delicate unpaired 

 nerve running between the dorsal apex of the frontal ganglion 



THE JOURNAL OF COMPARATIVE NErROLOGY, VOL. 26, NO. 5 



