546 CAROLINE BURLING THOMPSON 



Formica male: figure 37. Tract h is similar to that of the 

 queen. Tracts c and d are absent. Tract fl is similar to that 

 of the queen. Tract e is similar to that of other forms. Tracts 

 h, gl., gr., are homologous with those of all other forms. Tracts 

 m and p are similar to those of other forms. 



Lasius queen: figure 38. Tract h is homologous with h of other 

 forms, except that its origin cannot be traced beyond the pro- 

 tocerebral lobes, but the connection of h with fibers from all parts 

 of the mushroom bodies is especially well seen in this form. 

 Tract c is very prominent, and in addition to this is a new tract 

 ex, consisting of fibers from Group III, I. of the outer lobe. 

 Cx has been found only in the Lasius queen. Tract d is homolo- 

 gous with d of other queens, e is absent. Tract fl is a single 

 commissure homologous with fl of other forms. Tracts h, gl., 

 gr., m, p, are homologous with other forms. Tract r, from 

 Group III, I. of the inner lobe, is similar to tract r of the Formica 

 queen, the only other form in which this tract has been found. 



Lasius worker: figure 39. Tract h is homologous with other 

 forms in which the origin cannot be traced beyond the protocere- 

 bral lobes. Tracts c and d are absent. Tract e is slender but 

 typical. Tracts fl, h, gl., gr., m, are similar to those of other 

 forms. 



Lasius male: figure 4.0. Tract h is similar to all other forms 

 in which the origin is traceable only to the protocerebral lobes. 

 Tracts c and d are absent. Tracts e, fl, h, gl., gr., n, p, are similar 

 to those of other forms. 



10. THE ANTENNARY LOBES, OLFACTORY LOBES 



The antennary or olfactory lobes, the 'deutocerebrum' of Vial- 

 lanes, are paired lobes situated in the anterior and ventral surface 

 of the brain and connected on the dorsal surface with the proto- 

 cerebral lobes. In the three castes of ants the antennary lobes 

 are relatively about the same size, in proportion to the size of the 

 brain, being smaller in the always smaller male brain, or in a 

 small queen brain, for example, Formica. Judging by external 

 size, see figures 1 to 9, the antennary lobes of the castes of the 



