THE VENTRAL CORD. 2/7 



it is furnished with a large fleshy tongue, I could find neither lingual 

 nor labial nerves. In the caterpillar of Cossus ligniperda Lyonet 

 observed a connexion of the two labial nerves before they passed into 

 the labium ; from this point of connexion other branches originated, 

 which spread to the labium. Besides these the labium receives another 

 nerve (the same, f. 2. g, g.), which originates quite posteriorly, close to 

 the nerves of the maxilla 1 , and gives off in front of the labium an auxi- 

 liary branch for the muscles lying in the head. 



186. 



II. THE VENTRAL CORD. 



The ventral cord (medulla spinalis, s. venlralis) presents itself as a 

 consecutive series of ganglia, every approximate two of which are 

 united by one or two equal nervous cords. In the last case, conse- 

 quently, this ventral cord consists of two equal nervous threads, Avhich 

 from spot to spot are connected together, and form a common ganglion. 

 We have already spoken above of the structure of these ganglia and 

 threads, we will herf merely add that I have never detected a crossing 

 of the two threads in the ganglion ; they seem rather, upon their 

 entrance into it, to terminate, and the ganglion itself appears to con- 

 sist of a soft, uniform, granulated, nervous mass, which is enveloped 

 within a softer, frequently darker (for example, of a carmine colour in 

 the caterpillar of Noclua verbasci,) cortical substance. 



The numbers of the ganglia differ in the several orders and families, 

 but we may consider that there is properly one to every segment ; 

 hence their number would amount at most to thirteen, and we find, in 

 fact, this number in many larvae, namely, in all the larvae of the Lepi- 

 doptera. Two of these ganglia lie in the head, and form the brain, the 

 three following in the thorax, and the last eight in the abdomen. Each 

 of them sends off two or three radiating nervous filaments, which ori- 

 ginate at both its anterior and posterior extremities, diverge from each 

 other throughout their whole course, and distribute themselves to the 

 muscles, limbs, and several of the internal organs. 



O 



Besides the main cords which the ganglia form in conjunction, we 

 find between those which are chiefly seated in the segments of the thorax 

 other connecting filaments, as, for example, I have observed in the larva 

 of Calosoma si/cophanta, and shall therefore particularly describe. 

 The first pair of these auxiliary connecting filaments originates from 

 the posterior portion of the cerebellum (PI. XXXII. f. 1. B, h, h.), 



