BRAIN OF THE 'WHITE ANT' 565 



with round nuclei and a round cell body which appears as a 

 mere rim of cytoplasm (fig. 3, A,B), but in the .median dorsal 

 region, the intercerebral region of Haller, and here and there on 

 the ventral surface, the cells are larger with pear-shaped cell 

 bodies (fig. 3, C, D). The smallest nerve cells of the proto- 

 cerebral lobes are, however, almost twice as large as the adja- 

 cent nerve cells belonging to the mushroom bodies (fig. 3, E) 

 and to the optic lobes. 



In a series of frontal sections, beginning with the frontal or 

 anterior surface (figs. 13 to 20) it will be seen that the proto- 



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Fig. 3 Nerve cells from the protocerebral lohes and ihe mushroom body. 

 A, small cells, from the lateral region of the protocerebral lobes; B, medium 

 sized cells, from the same region; C, large cells, from the median ventral region 

 of the protocerebral lobes; D, large cells, from the intercerebral region; E, cells 

 from the mushroom bod}*. Homog. immers. 1.8 mm., oc. 6. 



cerebral lobes are at first entire (fig. 13), then, farther back in 

 the series (fig. 14) the two great anterior roots of the mushroom 

 bodies penetrate deep into the fibrous core of the protocerebral 

 lobes, dividing them into a median and two lateral portions, and 

 this division is further continued by the stalks of the mushroom 

 bodies (figs. 15, 16). 



a. The protocerebral comiiiissures. About the middle of the 

 protocerebral lobes, in the plane of the central body (fig. 15) the 

 lateral and median parts of the lobes are again connected by a 

 stout fiber tract passing from side to side beneath the central 

 body and connected also with the antenna! lobes. This tract 

 or commissure is homologous with the so called 'ventral com- 



