22 COMPAKATIVE ANATOMY. 



The supra-cesophageal mass consists, as usual, of two cephalic 

 ganglia, from which are derived the nerves which supply the 

 eyes. These ganglia are connected with the ventral cord by a 

 double nervous cord encircling the oesophagus. Three large 

 ganglia supply the thorax. The first pair of abdominal ganglia 

 are very large, but the remaining six, with the exception of the 

 last, are small. This ganglion sends off a bundle of nerves which 

 supply the segments posterior to it. 



3(j. A Common Cockchafer (Melolontlia vulgaris), female, 

 dissected to shew its generative and digestive systems, which 

 have been arranged on the left and right sides of the tablet 

 respectively. 



Generative organs. Each ovary is composed of a single 

 fasciculus of egg-bearing caeca. These cseca, or tubules, at their 

 commencement are small and slender, but as they descend they 

 dilate and assume a granular appearance, eventually fusing to 

 form the oviduct. The caBca composing the right ovary have 

 been partially separated. The two oviducts combine to form 

 the common vaginal canal, which opens externally. On the 

 right of the 'vagina,' and opening into it by a short duct, is the 

 pyriform 'speraiatheca:' on the same side and with the same 

 termination is the glandular accessory caecum. 



Digestive system. This is seen to be a canal of great length 

 in proportion to the size of the insect, of tolerably uniform 

 diameter throughout, and much convoluted. 



2. Order Orthoptera. 



37. A Common Cock-Roach (Periplaneta orientalis), dis- 

 sected to shew its digestive system. 



The oesophagus opens into a large pear-shaped crop. On 

 either side of the oesophagus may be seen the two-lobed salivary 

 gland. Posterior to the crop, and separated from it by a slight 

 constriction, is the muscular gizzard. The true chylific stomach 

 which succeeds receives at its anterior extremity a whorl of 

 eight casca; and a cluster of much longer and more slender 

 tubules is similarly arranged round its lower end. The first 

 eight caeca are regarded as analogous to the liver of higher 

 animals, while the tubules are probably renal. The ' colon,' 



