THE EMBRYOLOGY OF THE HONEY BEE 159 



nerve tissue thus formed is lower and longer in an anteroposter- 

 ior direction than the rudiment of the frontal ganglion, and is in 

 contact with the latter. This third mass forms the pharyngeal 

 ganglia of the stomatogastric system and possibly a part of the 

 frontal nerve connecting these ganglia with the frontal ganglion. 



The frontal ganglion is known to arise from a median evagina- 

 tion of the dorsal wall of the stomodaeum in Orthoptera (Vial- 

 lanes 1891, Wheeler 1893, Heymons), Forficula (Heymons 1895), 

 Coleoptera (Heider 1899), Hymenoptera (Carriere 1890) so that 

 it is safe to assume that this mode of origin is typical for the 

 insects. The accounts of Heymons and of Carriere and Burger 

 of the origin of the frontal ganglia and its associated structures 

 are the most complete and circumstantial. In Forficula and sev- 

 eral of the Orthoptera the stomatogastric system consists of the 

 frontal ganglion, close behind which is the elongate occipital 

 ganglion connected with the frontal ganglion by the short nervus 

 recurrens (stomatogastric nerve). From the occipital ganglia two 

 nerves run dorsad and caudad for a short distance to the paired 

 ganglia pharangea (pharyngeal ganglia), and these in turn send 

 out nerves which run to the posterior termination of the 

 oesophagus. 



The stomatogastric system in Chalicodoma (Carriere and Bur- 

 ger (1897) is essentially similar to that of the honey bee, consist- 

 ing simply of a frontal ganglion, a recurrent (stomatogastric 

 nerve) and a pair of pharyngeal ganglia. 



On comparing the stomatogastric system of these two repre- 

 sentatives of the Hymenoptera with that of Forficula and Gryllus 

 it becomes evident that the principal difference between them 

 lies in the apparent absence of the occipital ganglion in the repre- 

 sentatives of the Hymenoptera. In both the mason bee and the 

 honey bee the stomatogastric nerve is surrounded by ganglion 

 cells for some distance caudad of the frontal ganglia, and this 

 part of the nerve may therefore readily be homologized with the 

 occipital ganglion, as Carriere and Burger have already stated. 



The mode of origin of the stomatogastric system in Forficula 

 and Gryllus differs slightly from that in the honey bee. Three 

 evaginations are found on the dorsal wall of the stomodaeum. 

 From the first of these is formed the frontal and occipital ganglia, 



