574 CAROLINE B. THOMPSON 



VII. The antennal lobes 



The antennal lobes compose the deutocerebrum, or the second 

 brain segment, and are continuous with the anterior and ventral 

 part of the protocerebrum (fig. 2, a.L). In form they are elon- 

 gated masses that continue into the antennae as the antennal 

 or olfactory nerves. On their inner lateral surfaces the antennal 

 lobes are continuous with the third brain segment, the trito- 

 cerebrum. 



In sections it may be seen that the antenna! lobes have an 

 outer nerve cell layer containing both large and small cells, and 

 an inner fibrous core that contains scattered masses of glia cells, 

 the so-called 'gjomeruh.' 



The relative size of the antennal lobes differs very slightly in 

 the different castes of L. flavipes (figs. 8 to 12). The antennal 

 lobes are largest in the nymphs with long wing pads and in the 

 worker, but are smaller in the nymph with short wing pads and 

 in the soldier. Holmgren states that these lobes are much larger 

 in the worker of Eutermes than in the other castes: "die Deuto- 

 cerebralganghen der Arbeiter sind verhaltnissmassig grosser und 

 enthalten eine auch absolut bedeutend grossere Zahl GangUen- 

 zellen als bei den Geschlechtsindividuen." 



VIII. The tritocerehral lobes and the tritocerebral co7nmissure 



The tritocerebral lobes are small lobes extending ventrally 

 along the sides of the esophagus and continuous with the inner, 

 lateral, surfaces of the antennal lobes (fig. 20). From the inner 

 median surfaces of the tritocerebral lobes arise a pair of nerves 

 that ran forward alongside of the esophagus and unite in the 

 frontal ganglion; these are the tritocerebral or labrofrontal nerves 

 (fig. 2, l.f.n.). Beneath the esophagus the tritocerebral lobes 

 unite in the slender tritocerebral commissure (fig. 2, tr.cm.), 

 which is almost devoid of any investing nerve cells. 



IX. The frontal ganglion 



The frontal ganglion is a small mass of nerve tissue situated 

 just beneath the clypeus, the sclerite of the head to which the 

 labrum is attached, and above the mouth opening, somewhat 

 antero-ventral to the brain (figs. 2, S,fr.gn.). 



