CHAP. II.] 



A NERVOUS SYSTEM. 



51 



the two pairs of gan- 

 glia of Eolis. Thus 

 median compound 

 ganglia (fig. 18, g) 

 are formed, connected 

 with one another by 

 single, or it may be 

 by double (e, li) com- 

 missures. The ter- 

 minal double group 

 (A) represents the 

 brain of the animal, 

 and this is probably 

 capable of receiving 

 stimuli by some fibres 

 from the sensory por- 

 tion of each single or 

 double ganglion 

 throughout the body 

 of the Insect. It can 

 probably also transmit 

 motor stimuli along 

 other commissural 

 fibres to each motor 

 division of the same 

 body ganglia. 



In the Grasshopper 

 the brain is not more 

 than three or four 

 times as large as one 

 of the compound gan- 



.... . . FIG. 18. Nervous system of the Great Green 



glia 111 Communication Grasshopper (Newport). A, brain ; B, optic nerves ; 



with tllP IPCTCJ 1 ^' an *ennal nerves ; d, motor nerve of mandible 



from sub-cesophageal ganglion ; g, first thoracic gan- 



WlllgS. glion, connected to the second, as the second is to 



T -TT , i . the third, by two commissures. 



In Vertebrate Am- _ 



lli A 



