MUSHROOM BODIES OF BOMBUS 287 



commissure, that is, cm^ving out of the vertical plane, and passing 

 to the fibrous core side by side and together with the commissure 

 fibers, making what he aptly calls a ''chiasmatische Bahn." It 

 is not surprising that this difference should occur between Bombus 

 and Apis mellifica, since in ants a great variety in structure exists 

 between different genera and even between the castes of one genus, 

 Thompson, 1913, page 531: 



To summarize: in ants the ocellar nerve fibers may take three differ- 

 ent paths from the ocellar lobes: (1) by way of the anterior dorsal com- 

 missure, queens of Lasius and Camponotus, (2) through the posterior 

 commissure, Formica queen, Formica and Lasius workers, (3) both 

 through and by way of the posterior dorsal commissure, males of the 

 three genera. 



Since the fiber tract in question is an '^Ocellarnervenbriicke," 

 or path for the ocellar nerves, only in certain cases, but is invari- 

 ably the ''posterior dorsal commissure," the latter term has a 

 better excuse for existence than the former. The writer trusts 

 that the name " Ocellarnervenbriicke " may be cast away together 

 with " protocerebral nerve bridge," "ocellar glomeruli," and "tu- 

 bercles of the central body." 



The origin of the posterior dorsal commissure in Bombus is 

 from the protocerebral fibrous core, figure 8, as in ants, and does 

 not arise from cells of the intercerebral region as Jonescu states 

 is the case in Apis mellifica. 



February 27, 1914. 



BIBLIOGRAPHY 



VON Alten, H. 1910 Phylogenie des Hymenopteran Gehirns. Jenaische Zeit- 

 schr., Bd. 46. 



Jonescu, C. 1909 Vergleichende Untersuchungen iiber das Gehirn der Honig- 

 biene. Jenaische Zeitschr., Bd. 45. 



Thompson, C. B. 1913 A comparative study of the brains of three genera of 

 ants, with special reference to the mushroom bodies. Jour. Comp. 

 Neur., vol. 23, no. 6. 



