226 THE ROYAL SOCIETY OF CANADA 



central nervous system consists of the supra-oesophageal ganglion or 

 brain and the ventral chain. The latter is situated along the median 

 line of the venter, above the ventral muscles. The first ganglion of 

 the ventral chain (the sub-oesophageal ganglion) is joined to the brain 

 by a pair of connectives which pass around the oesophagus, so that 

 the entire nervous system is composed of a chain of ganglia giving 

 off nerves, each ganglion connected with the one on either side of it by 

 a pair of connectives. 



In describing the central system below, the ganglia and nerves 

 situated in the head will first be described, then those of the thorax 

 and lastly, those of the abdomen. The sympathetic systems will be 

 described separately. 



Acknowledgments. To Mr. J. M. Swaine of the Division of 

 Entomology, Ottawa, at whose suggestion this investigation was 

 undertaken, I am indebted for valuable hints as regards methods, 

 given me at the inception of the work. I also wish to express my 

 gratitude to Professor William Lochhead for his generosity in placing 

 at my disposal his library and the splendid equipment of the Biolog- 

 ical laboratories of Macdonald College, and to Professor A. D. Mac- 

 Gillivary of the University of Illinois, for kindly reading this paper 

 in manuscript and making several valuable suggestions. 



Methods. 



The plants containing the caterpillars were cut off about nine 

 inches above the ground in the late fall, and the lower portions dug 

 up, brought indoors and planted in wet sand. The caterpillars were 

 removed as needed. Several specimens were also preserved in 5% 

 chloral hydrate. 



The usual methods of dissection were followed. The insect was 

 first etherized, then cut along the median line of the dorsum and 

 pinned under water in a small dissecting tray. The pins were then 

 cut off close to the insect in order that they might not interfere with 

 the free manipulation of the dissecting instruments. The abundance 

 of adipose tissue is a great hindrance in dissecting and to remove it 

 without breaking the nerves required careful and patient mani- 

 pulation. 



On account of the transparency of the fresh tissues it was found 

 necessary to fix or stain the material before tracing the course of the 

 nerves. 



Fixing. Gilson's alcoholic sublimate gave good differentiation 

 but was not found convenient for use in dissecting on account of the 

 corrosive action of the mercuric chloride on metals. 



