204 LECTUKE XVI. 



main of physiology at that period ; and it was a great advantage to 

 Zootomy that Lyonnet looked at his subject with the eye of truth, 

 and not through the prism of any pre-formed physiological notions. 



The supra- oesophageal ganglion gives off ten nerves ; eight in pairs, 

 and two solitary or azygos nerves ; one of these latter is the anterior 

 oesophageal ring, which Mr. Newport has figured and described in 

 the Sphynx ligustri. Its extremities are connected with the cephalic 

 ganglion immediately anterior to the attachment of the principal 

 columns which form the posterior oesophageal ring. The second 

 solitary nerve is sent off from the middle of the posterior side of the 

 cerebral ganglion, and proceeds backwards to the oesophagus. The 

 cephalic nerves, sent off in pairs, supply the antennae, the ocelli, the 

 muscular and integumentary parts of the head, and communicate 

 with branches of the maxillary nerves. The most remarkable pair, 

 however, is that which arises anterior to the annular or oesophageal 

 nerve, and which constitutes the cephalic roots, or connections of the 

 stomato-gastric system. Each of these nerves passes forwards and 

 divides ; the external tract joins one of the maxillary nerves of the 

 suboesophageal ganglion. The internal one converges towards its 

 fellow, and terminates with it in the first of the median cephalic series 

 of ganglions, Avhich Lyonnet terms frontal ganglions. The longest 

 nerve in the whole body of the caterpillar is given off" from these 

 ganglions as it passes along the oesophagus to the stomach and in- 

 testines : it w^as called by Swammerdam the recurrent nerve. There 

 are two other small ganglions situate in the head of the caterpillar on 

 each side of the large bilobed or cephalic ganglion. The largest 

 nervous columns connected with the supra-oesophageal ganglion, are 

 those which enclose the oesophagus by uniting with the first of the 

 lower series of ganglions. From this ganglion nerves are distributed 

 to the mandibles, the maxillae, the lips, and their special organs of 

 sensation or palpi. Two distinct diverging columns connect the first 

 wdth the second ventral ganglion ; and this is similarly connected with 

 the third. The inter-communicating chords of the remaining gan- 

 glions appear single at their anterior part, and bifurcate as they are 

 connected with the next ganglion in succession. They are of a 

 greyish blue but transparent colour, and are very elastic. From 

 each side of the abdominal ganglions are given off two principal 

 branches ; the anterior to the muscles chiefly, the posterior chiefly to 

 the integuments^, but communicating with the muscular branch of the 

 succeeding ganglion. From the beginning of the separation of the 

 bifurcated inter-ganglionic columns, or conduits, Lyonnet says, "^ there 

 descends a nerve, the extremity of which is enlarged a little above the 

 succeeding ganglion, which sends off from the enlargement a trans- 



