BRANCH ARTHROPOD A; CLASS MSECTA : THE INSECTS 185 



which may be called the aorta. There are no other 

 arteries or veins, the blood simply pouring out of the 

 anterior end of the dorsal vessel into the body-cavity. It 

 bathes the body tissues, flowing usually in regular channels 

 without walls. It re-enters the dorsal vessel through 

 paired lateral openings in the chambers. 



The main or central nervous system consists of a large 

 ganglion, the "brain," situated in the head above the 



FIG. 49. A section through the compound eye (in late pupal stage) of the 

 blow-fly, Calliphora romitoria. In the centre is the brain, with optic 

 loin-, and on the right-hand margin are the many ommatidia in longi- 

 tudinal section. (Photo-micrograph by Geo. O. Mitchell.) 



oesophagus, which sends nerves to the antennae and eyes > 

 a ganglion in the head below the oesophagus connected 

 with the brain by a short commissure on each side of 

 the oesophagus, and sending nerves to the mouth-parts ; 

 and a ventral nerve-chain composed of a pair of longitudinal 



