104 NERVOUS SYSTEM OF ARTHROPODS. 



ment of those portions of it in relation with the visual 

 organs, as may be seen by fig. 45, representing the nervous 

 system of the Common Fly, and by fig. 42, representing 

 the brain of a Beetle. A ganglionic swelling is fre- 

 quently found where the optic nerve joins the brain, and 

 in some Insects there are also small ganglionic swellings 

 at the corresponding parts of the antennal nerves. 



It is in Ants, Bees, and Flies, however, that the brain 

 of Insects seems to attain its greatest development. Speak- 

 ing of the brain of the Blow-fly, B. T. Lowne says* : 

 " Next to bees and ants that of the blow-fly is the largest 

 known in any insect proportionally to its size, being about 

 thirty times larger than the cephalic ganglia of the larger 

 beetles." The same writer adds : " But a more positive 

 indication of a higher type of organization than even the 

 relative bulk of the sensory ganglia is found in the fact 

 that two very remarkable convoluted nerve centres, con- 

 nected by a commissure, each about l-30th of an inch in 

 diameter, surmount the cephalic ganglion, and are con- 

 nected to it by a pair of distinct peduncles ; t these are 

 extremely like the pedunculated convoluted nerve centres 

 which occupy the same position in bees and ants, first 

 described by M. Felix Dujardin (" Ann.des Sc. Nat." (Ser. 

 in.), t. xiv. p. 195), and considered by him as analogous to 

 the cerebral lobes of the higher animals. That naturalist 

 failed to distinguish these organs in the fly, probably 

 owing to their being imbedded in the substance of the 

 cephalic ganglion." In the Bee, according to Dujardin, 

 these peculiar bodies are attached to the sensory ganglia 

 by a single peduncle, and their united bulk is said by 

 him to equal -J-th of the whole brain. Farther details 

 concerning these interesting structures are much needed. 

 The double cerebral ganglion is connected in nearly 

 * " Anat. of the Blow-fly," p. 14. f LOG. cit., PI. vii. fig. 4. 



