NERVOUS SYSTEM. INVERTEBRATA. 41 



D. 37. A Lamellicorn Beetle (Dynastes centaurus) dissected from 

 above to show the nervous system. The cerebral ganglion 

 is comparatively small ; it is united to the suboesophagcal 

 by connectives of moderate length. In the thorax there; 

 are three ganglionic masses, of which the anterior two are 

 simple and respectively constitute the pro- and meso- 

 thoracic ganglia ; the posterior mass is elongated in shape, 

 and consists of the true rnetathoracic ganglion fused with a 

 short cylindrical appendage that represents a concentra- 

 tion of the abdominal chain ganglia, and innervates the 

 abdomen. This arrangement of the ganglia is the one 

 usually found among Lamellicorns. 



D. 38. A male Longicorn Beetle (Macrotomci) showing the 

 nervous system from above. The cerebral ganglion is 

 small relative to the head, and is united to the subcesopha- 

 geal ganglion by long connectives. The thoracic ganglia 

 are separate, with approximation between the ineso- and 

 metathoracic. The latter innervates the anterior part of 

 the abdomen, as well as the metathorax. There are four 

 free abdominal ganglia, the first of which is situated on 

 the boundary-line between the thorax and the abdomen. 

 This number and arrangement of the ganglia is charac- 

 teristic of this family of Beetles. 0. C. 1299 A. 



D. 39. The nervous system of a Hornet ( Vespa crabro), isolated. 

 The large size of the cerebral ganglion is due, partly to the 

 bulk of the protocerebral lobes the centres for the great 

 compound eyes, and partly to the high degree of develop- 

 ment of the fungiform bodies. The latter differ in 

 many respects from those of the Black-beetle (D 27) ; 

 their calyces are larger and arch to a considerable extent 

 over the anterior and posterior surfaces of the proto- 

 cerebral lobes ; the peduncle and its two calycal branches 

 are remarkably stout, but the cauliculus and trabecula are 

 insignificant, and without definite outlines. The ocelli 

 receive their nerves from three centres that lie directly 

 beneath them. The cerebral ganglion is continuous around 

 the oesophagus with the small suboesophageal ganglion. 

 There are two ganglia in the thorax the first is the pro- 



