ON THE BRAIN OF THE COCKROACH. 347 



the base of this, and close to the ganglion itself, a minute 

 nerve is given off, which, passing directly outwards, could be 

 traced to the proximal part nf the stipes. Further down the 

 maxillary neive divides into two, and then the outer division 

 into two again, thus forming three branches, which no doubt 

 supply the three distal divisions of the maxilla. From the 

 front and lower part of the ganglia, two large nerves pass 

 downwards and forwards, close together for some little dis- 

 tance, and then diverging, each passes into the mandible of 

 its own side. At the base of this nerve again, a minute 

 fibre arises, as in the case of the nerves of the maxilla and 

 labium, and this was found to pass into the mandible at its 

 most proximal part. Although the distribution of the fine 

 fibre accompanying the labial nerve could not be traced, it 

 seems probable that it supplies the basal portion of the la- 

 bium; and if such should prove to be the case, then each 

 of the mouth appendages will be seen to be supplied with 

 two nerves, a larger and a smaller one. 



At present I have been unable to trace any nerves or 

 nerve into the lingua. 



The stomato-gastric nerves, as stated above, arise by two 

 roots, one from each oesophageal commissure, which unite 

 in the frontal ganglion. The single ncrvus recurrens (fig. 

 ^ f 11), passing back from the frontal ganglion (figs. 1 and 

 2 f g.), runs along the oesophagus under the brain, and is 

 connected with the stomato-gastric ganglia, situated at the 

 back of the brain. The most successful dissection of these 

 ganglia which I have been able to make is represented in 

 fig. 4, but this has been verified by several other preparations. 

 It will be seen that the nervus recurrens becomes much 

 thickened at the point where it joins, on each side, a short 

 stem connected with the hinder end of an elongated, some- 

 what spindle-shaped, ganglion. Each of these ganglia is 

 connected posteriorly with a second oval ganglion, and ante- 

 riorly a short bundle of fibres connects it w-ith the back part 

 of the brain. In one or two dissections I could trace these 

 nerves some little way under the back of the brain, but 

 failed to convince myself as to whether they joined the brain 

 or not ; however, in another dissection of a very large cock- 

 roach, these nerves could be seen joining the back of the 

 brain well underneath, but no nerve could be traced passing 

 forward from this point. Nervous filaments are given off 

 from the posterior pair of ganglia ; and in another prepara- 

 tion fibres were seen to be given off from the anterior pair 

 also. 



In the Sphynx moth, according to Newport (' Phil. Trans./ 



