BRAINS OF THREE GENERA OF ANTS 545 



be the same as p of other forms, that is, some of its fibers may 

 come from Group IV as well as from III, but since no con- 

 nection with Group IV could be seen, it has been classed as a 

 separate fiber tract and is separately lettered. 



Camponotus male: figure 3 If.. Tract h is homologous with that 

 of the queen. Its origin cannot be traced to the mandibular lobe 

 as in the case of the worker. Tract c is similar to that of the queen. 

 Tract d is absent. Tract fl is similar to that of the worker. 

 Tracts e, h, gl., gr. are homologous with those of both queen and 

 worker. Tracts m and n are absent. Tract p is a slender fiber 

 bundle which arises from both Groups III, r and IV, r of the 

 outer lobe, and leaving the stalk, enters the outer part of the 

 protocerebral lobes. 



Formica queen: figure 36. Tract h is well developed and is 

 homologous with h of the other forms. Its origin cannot be traced 

 beyond the protocerebral tissue. Tract c has a slighter develop- 

 ment in Formica than in either of the other queens. It exists 

 merely as a few delicate strands coming from the inner cup rim 

 of the inner lobe and entering the protocerebral tissue together 

 with the outer Hmb of h. Tract d is homologous with d of 

 the other queens, fl is homologous with that of the Campono- 

 tus worker and male, e is absent from this caste. Tracts h, 

 gl., gr., are similar to those of all the other castes and genera. 

 Tract m, though present is very slender, tract p is similar to p 

 of other forms. A new tract, r, is seen for the first time in this 

 form. It arises from Group III, I, of the inner lobe and runs 

 down the outer surface of the stalk of this lobe. 



Formica worker: figure 36. The origin of h from a stout 

 bundle of fibers that is traceable to cells in the cortex of the 

 mandibular lobe is more distinct in the Formica worker than in 

 any other form. Tracts c and d are absent, e is slender and delicate 

 but distinct. F and Z are two fiber tracts which are present in 

 the same three sections, and unite the inner and outer lobes, / 

 dorsal to I. With the exception of the fact that these two tracts 

 occur one above another in the same sections they are exactly 

 similar to / and I of the Camponotus queen. Tracts h, gl., 

 gr., m, and p are similar to those of other forms. 



