PLATE 4 



EXPLANATION OF FIGURES 



Figures 17 to 20 are consecutive sections from a frontal series of the head of the 

 queen of Lasius niger; figure 21 is two sections behind figure 20. Oc. 4, obj. AA, 

 Zeiss. 



17 Section showing the fibrous core of the protocerebral lobes, the anterior 

 dorsal commissure, a.cm., the outer ocellar lobes, o.oc.L, wiiose fibers pass into 

 the commissure, and the distal ends of the stalks of the mushroom bodies, st., 

 partly divided into two bundles. 



18 Section showing the complete division of the stalks into two bundles, two 

 dorsal bundles, d.b., fibers from which are entering the central body, and two 

 ventral bundles, the posterior roots of the mushroom bodies, v.b. {p.r.). The an- 

 terior commissure is no longer present. 



19 Section showing the entrance of fibers from the dorsal bundles into the 

 central body, c.b., which is disappearing. 



20 Section showing the central part of the posterior commissure, p.cm., and 

 the posterior roots, p.r., which are about to enter the protocerebral fibrous core. 



21 Section showing the lateral ends of the posterior commissure, p.cm., and 

 the posterior roots, p.r., now within the fibrous core. 



22 Camponotus male. Section showing the posterior commissure, p.cm., the 

 posterior roots, p.r., within the protocerebral fibrous core, and the ocellar nerve 

 fibers passing down from the four ocellar lobes. Oc. 4, obj. AA, Zeiss. 



23 Formica, queen. Section showing the entrance of fibers from the outer 

 ocellar lobes, o.o.l., down through the posterior commissure, p.cm. Oc. 4, Obj. 

 AA, Zeiss. 



566 



