568 CAROLINE B, THOMPSON 



zones of nerve cells just described, and (2) of masses of glia cells 

 (fig. 4, gl.) resembling the 'glomeruli' of the antennal lobes, which 

 envelop the fiber bundles -on all sides and unite the calyces of 

 the two lobes into one continuous whole. 



The stalks of the mushroom bodies are the continuations 

 downward and inward of the fiber bundles of each lobe. These 

 lie side by side, the fibers from the inner lobe on the median side 

 of those from the outer lobe, and for a short distance they remain 

 distinct. The two stalks, surrounded by a dehcate sheath, pene- 

 trate deep down into the fibrous core of the protocerebral lobes 

 and then run forward. There is no 'decussation' of fibers such 

 as is seen in the hymenoptera. In the same frontal plane with 

 the central body (fig. 15) the distal ends of the stalks lie beneath 

 the central body, and at this point each stalk gives rise to three 

 roots, the anterior, the central body, and the posterior roots. 

 The central body roots, which are the shortest, pass upward and 

 directly into' the central body (fig. 16, c.h.r.). The anterior roots 

 which are the longest, bend sharply upward and forward, mak- 

 ing an elbow with the stalks from which they have arisen (fig. 

 14, a.r.m.b., m.b.s.). In sections that are farther forward in the 

 head, the anterior roots may be seen as two great bundles of 

 fibers curving latero-dorsally and dividing the protocerebral lobes 

 in the manner already described. On reaching the dorso-lateral 

 margins of the protocerebral core, the anterior roots curve in a 

 posterior direction and are seen in sections as two detached 

 masses on the outer sides of the mushroom bodies (figs. 15, 16, 

 a.r.m.b.), then (fig. 14) returning again forward, the narrow dis- 

 tal ends turn downward and terminate among the nerve cells 

 of the anterior part of the protocerebral lobes. 



The posterior roots branch off from the stalks together with 

 the central body roots, and, after the latter have passed into 

 the ventral surface of the central body, pass dorsalward, posterior 

 to the central body and to the posterior dorsal commissure, there 

 expanding into two large and very prominent lobes which nearly 

 fill the intercerebral region (figs. 19, 20, 23, 26, p.r.m.b.). The 

 ventral part of these lobes or roots is connected with the proto- 

 cerebral fibrous core, the dorsal part, however, projects back- 



