

THE OLFACTORY LOBES 



237 



cellos 



formed entirely of a pi 



, ... mushroom body. 



fine and close nbrillar 



FIG. 254. Section through the brain of Calopte- 

 nus bivittdlus in the third larval stage, showing the 

 two hemispheres or sides of the brain, and the ocelli 

 and ocellar nerves, which are seen to arise from the 

 top of the hemispheres directly over the calices (com- 

 pare Fig. 251) : o. cal, outer division of calyx of left 



The result of our studies on the brain of the embryo locust was 

 that from the embryonic cerebral lobes are eventually developed 

 the central body and the two mushroom bodies. Fig. 254 shows 

 the early condition of the 

 mushroom bodies and their 

 undoubted origin from the 

 cerebral ganglia. Hence these 

 bodies appear to be differ- 

 entiations of the cerebral 

 ganglia or lobes, having no 

 connection with the optic or 

 antennal lobes. 



The central body (Fig. 252, 

 centr. 6). This is the only 

 single or unpaired organ in 

 the brain. Dietl characterizes 

 it as a median commissural 

 system. Viallanes describes 

 it as 

 very 



web, like a thick hemispherical skull-cap, situated on the median 

 line and united with the cerebral lobes. " It is like a central post 

 towards which converge fibres passing from all points of the brain ; 

 being bound to the cerebral lobes, to the stalked bodies, to the optic 

 ganglia, and to the olfactory lobes by distinct fibrous bundles." 



The antennal or olfactory lobes (Deutocerebrum). This portion of 

 the brain consists of two hemispherical lobes, highly differentiated 

 for special sensorial perceptions, and connected by a slightly differ- 

 entiated medullary mass, the dorsal lobe (Figs. 248, 249 lo), from 

 which arise the motor fibres and those of general sensibility. The 

 antennal lobes are in part attached to the optic ganglia, and partly 

 to the stalked body on the same side, by the optic olfactory chiasma 

 (Fig. 250 /c/i, c/ioo), a system of fibres partially intercrossed on the 

 median line. 



The oasophageal lobes (Tritocerebrum) (Figs. 249, 250). From this 

 region the labrum and viscera are innervated, the nerves to the latter 

 being called the visceral, sympathetic, or stomatogastric system. As 

 Viallanes remarks, though plainly situated in front of the mouth, 

 they are in fact post-oesophageal centres. The two lobes are situ- 

 ated far apart, and are connected by a bundle of fibres passing 

 behind the oesophagus, called the transverse commissure of the 

 cesophageal ring (Lienard). The cesophageal ganglia, besides giving 



