TR ACHE AT A 



329 



of breathing, and the consequent absence of a respiratory 

 function of the blood, has taken place concurrently with the 

 formation of a new method of ridding the body of its waste 

 nitrogenous matter. In most other Coelomata this is effected 

 either by means of tubules ultimately ending in flame cells, or 

 by nephridia, and these two methods are connected by inter- 

 mediate forms ; but in the true Tracheata the nitrogenous 

 matter leaves the body by caecal diverticula of the alimentary 

 canal, formed usually from the proctodaeum, but sometimes 

 from the mesenteron. These Malpighian tubules receive the 

 matter they are to excrete either at first hand from the blood, 

 or the urates, etc., have been stored for a time in the cells of a 

 mesoblastic tissue, the fat-bodies, and, when these disintegrate, 

 the nitrogenous matter is carried by the blood to the tubules, 

 and thence passes through the rectum to the exterior. 



The nervous system of Melolontha is very concentrated, 

 instead of the double nerve cord enlarging into a ganglionic 



FiQ. 188. — View of nervous system of Melolontha 

 vulgaris. After Vogt and Yung. 



9. 



10. 



Ceretral ganglion. 



Sub-oesophageal ganglion. 



1st thoracic ganglion. 



2nd thoracic ganglion. 



3rd thoracic ganglion. 



Fused abdominal ganglia. 



Nerves to antennae. 



Optic nerves. 



Origin of sympathetic nerves. 



Abdominal nerves, a pair to each segment, 



which split into an anterior and posterior 



branch. 



mass in each segment, the ganglia are to a great extent fused 

 into a central mass, from which the nerves radiate. 



The supra-oesophageal ganglion occupies a considerable part 

 of the head ; it consists of two well-marked lobes separated by 



