THE POSTERIOR ROOTS OF THE MUSHROOM BODIES 

 IN THE WORKER OF BOMBUS SP. 



CAROLINE BURLING THOMPSON 



From the Department of Zoology, Wellesley College 



EIGHT FIGURES 



The present study has been made to determine whether the 

 relation between the posterior roots of the mushroom bodies and 

 the central body is the same in the bumble bee as in the ants 

 previously described, Thompson, 1913. 



The material, consisting of the brains of the adult workers of 

 Bombus sp., was collected in August, 1913, in Wellesley, Mass. 

 The heads were removed from the body, and before being placed 

 in the fixative, Gilson's fluid, cuts were made in the epidermis. 

 After fixation and hardening the heads were opened and the 

 brains dissected out and embedded in paraffin. The sections 

 were about 9^ thick and were stained in Ehrlich's hematoxylin 

 and eosin. 



The series of cross sections drawn in figures 1 to 8 trace the 

 course of both the central body roots and the posterior roots of 

 the mushroom bodies, and show the relation of these roots to the 

 central body, to the ocellar nerve fibers, and to the posterior 

 dorsal commissure. 



Figure 1 is from a section through the posterior part of the main 

 stalks of the mushroom bodies, st., and through the posterior 

 region of the central body, c.b. The two parts of the central body 

 are shown : the upper, large and fan-shaped, consisting of masses 

 of fibers in transverse section alternating with radial and inter- 

 lacing bundles in longitudinal section ; the lower part smaller, and 

 also containing fibers that are radially arranged. Fibers may be 



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THE JOURNAL OF COMPARATIVE NEDROLOGT, VOL. 24, NO. 3 



