NO. 8 MORPHOLOGY OF INSECT SENSE ORGANS SNODGRASS 



II 



together association fibers from all parts of the brain and the 

 ventral cord. 



The mushroom bodies, apparently, have no counterparts in any 

 of the ganglia of the ventral cord. Each consists of a double fibrous 

 stalk (fig. 5, h), buried in the lateral lobe of the protocerebrum, 

 and of two cup-like fibrous masses, the calyces {a, a), supported on 

 the ends of the stalks in the dorsal part of the brain. The calyces 

 are filled with nerve cells (c), the axons of which (/) penetrate 

 the stalks of the bodies and give ofif finely-branching collaterals 

 (c) into the tissue of the calyces. At the lower end of the stalk 

 of each body the fibers separate into a ventral and an anterior 

 root. The mushroom bodies receive association fibers (d) from 



Fig. 5. — Diagram of a " mushroom body," or corpus pedunculatum, 

 of the brain. 



a, a, calyces; b, stalk; c, calyx cells giving axons (/) into the stalks, 

 and collaterals (e) into the neuropiles of the calices ; d, association 

 fibers from other parts ending in arborizations within the calices. 



nearly all other parts of the brain, from the suboesophageal gan- 

 glion, and from the other ganglia of the ventral nerve cord, most of 

 which end' in fine branches within the calyces. If the insect, there- 

 fore, has intelligence, or consciousness of external things that afifect 

 it, or of its own actions, the seat of this faculty must surely be in 

 the mushroom bodies. Or, if insects are but living mechanisms, 

 the chief regulatory centers must again be these bodies, which are 

 to the ganglia what the ganglia are to the peripheral nerves — they 

 are the centers of the central nervous system. The mushroom 

 bodies appear to be present in nearly all insects, but they are much 

 more highly developed in the Diptera and Hymenoptera than in 

 the lower orders. 



The first division of the brain, the protocerebrum (fig. 4, i Br), 

 supports the simple and the compound eyes, but a discussion of 

 the optic tracts and the ocellar nerves is omitted here because the 



