THE EMBRYOLOGY OF THE HONEY BEE 149 



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FIG. 56. Transverse section through head of an embryo, Stage XIII- 

 XIV. This section passes just caudad of the antennal rudiments, x 387. 



reference to the rest of the brain, the outermost of the three 

 divisions of the protocerebral lobes (see pp. 116-117). Since in the 

 honey bee these lobes are, with reference to the poles of the egg, 

 directed caudad and laterad, the optic lobes may be similarly 

 described as derived from the lower and posterior border of the 

 protocerebral lobes, although this is actually their upper (dorsal) 

 and anterior border. As in other insects then development differs 

 from that of the remainder of the brain. 



At Stages VIII and IX the ectoderm destined to form the optic 

 lobes is not distinguishable from the other neurogenic ectoderm 

 of the brain rudiment. During the succeeding stages the greater 

 part of the latter becomes transformed into neuroblasts and gang- 

 lion cells and the regular palisade-like arrangement of its cells 

 altogether disappears. This does not occur in the region of the 



