FSYCHE. 



ON THE NERVOUS SYSTEM OF THE HEAD OF THE 

 LARVA OF CORTDALUS CORNUTUS LINN. 



IIY WILLIAM CHRISTOPHER KRAUSS, ATTICA, N.Y. 



[With Plate 2.] 



[Extract from n thesis in cntomologVt presented to the Faculty ofthe Cornell university for the 

 Baccalaureate in science.] 



The nervous S3'stcm of the head of the 

 larva of Co?-ydah/s cornutus Linn., con- 

 sists of — 



I. The supra-oesophageal ganghnor 

 cerebrum, and nerves. 



3. The crura cerebri. 



3. The sub-oesophageal ganglion or 

 cerebellum, and nerves. 



4. The commissures. 



5. Tlie vagus nerve. 



I. The SUPRA-OESOPHAGEAL GAN- 

 GLIA, OR CEREBRUM. — The supra-oes- 

 ophageal ganglia (fig. i. i) are situated 

 in the dorso-cephalad part of the head, 

 midway between the tips of the labruin 

 and the base of the head. They lie 

 dorsad of the oesophagus, and immedi- 

 ately entad of the dorsal body wall, be- 

 ing separated from it only by thin, deli- 

 cate layers of adipose tissue. 



The supra-oesophageal ganglia, the 

 probable homologs of the vertebrate 



cerebrum, tlifler greatly from the other 

 ganglia or nerve centres of the body. 

 They are a compound organ composed 

 of two distinct ganglia or hemispheres 

 connected together by a short, thick 

 commissure on the meson, but are some- 

 times described as a single ganglion. 

 These hemispheres are similar in out- 

 line, having an ovoid appearance. The 

 lateral ends of the hcmi,s]ihf'res taper 

 into the cerebral nerves. In the two- 

 year-old larva, the cephalo-caudal diam- 

 eter of the hemispheres is three-fourths 

 of a millimetre, and the two together 

 attain the length of two millimetres. 



The ventro-latero-cephalad borders ot 

 the cerebriun are developed ventrad, 

 forming the crura cerebri, which con- 

 nect it with the sub-oesophageal gan- 

 glion. 



The cephalad extremity of the aorta i.s 

 attached to the neurilemma, at tiie can- 



