THE VENTRAL CORI). 283 



coleopterous families with abdominal ganglia we find in general not 

 merely fewer than the first named instances, but also fewer than in 

 their larvae. During their metamorphosis, namely, either two ganglia 

 appear to grow together, or else some wholly disappear ; that may be 

 the reason why the ganglia of the thorax are larger than those of the 

 abdomen, at least the growing together of the third and fourth ganglia 

 of the larvae of the Coleoptera is very probable, particularly as this 

 union is proved to take place in the Lepidoptera during their meta- 

 morphosis by Herold's history of that state of them. We therefore 

 find in general in the perfected beetle only five ganglia, the two last of 

 which are drawn so closely together that they form an eight-shaped 

 ganglion. From each of these ganglia two undivided pairs of nerves 

 proceed, which are rarely ramose at their extremity, and which, as 

 well as the cord lying on the ventral plates, distribute themselves 

 among all the viscera of the abdominal cavity near the surface of the 

 plates. The radiating nerves of the last ganglion alone, which forms 

 the analogue of the cauda cquina of the superior animals, distribute 

 themselves to the internal sexual organs and to the colon. In Carabus, 

 Hydrophilus, Cerambyx, Lytta, and Meloe there are but these five 

 ganglia, and never more. 



Having observed in all these insects three distinct thoracic ganglia, 

 one for each thoracic segment, we now come to those orders and families 

 Avhich have but two separated ganglia in the thorax. In the Coleoptera 

 the large family of the Lamcllicornia belong here. The accurate 

 representation of the nervous system in Melolontha vulgaris in 

 Straus * exhibits a heart-shaped ganglion lying in the prothorax, from 

 which a robust nerve originates on each side, which speedily divides 

 into several branches, the central thickest of which passes to the 

 anterior leg, whereas the smaller ones distribute themselves between 

 the muscles of the prothorax. The second ganglion, lying in front of 

 the mesothorax, appears to consist properly of two closely contiguous 

 ones, at least the aperture perceived in its centre evidently indicates 

 an original separation. From the anterior division proceed the nerve of 

 the intermediate foot and several branches for the muscles, as well as a 

 nerve originating completely in front, which passes to the elytra ; from 

 the posterior division springs the nerve of the wing, which gives off 

 branches to the muscles and the nerve of the posterior leg, which like- 



* Straus, PL IX. 



