DISSECTION 161 



apophyses ; but it is doubtful whether these really 

 belong to the same category as the appendages of 

 the head and thorax. 



The gonapophyses belong to the genital appa- 

 ratus, and will be described later. 



m. DISSECTION OP THE COCKEOACH. 



Fix the animal down with the dorsal surface upwards. 

 This may be done by drying it with blotting paper, and 

 immersing its under surface in melted paraffin or wax, and 

 holding it in this position till the wax is cool ; or the animal 

 ma/y be fixed to a hoard by means of small pins passed through 

 the lateral regions of the mesothorax and of the abdomen. 



Cut off the elytra and the wings. Carefully cut through 

 the terga of the abdomen and thorax close to each side, and 

 remove the terga, avoiding injury to the heart, which lies just 

 beneath. 



A. The Circulatory System. 



1. The heart is a straight chambered tube running along 

 the mid- dorsal line of the abdomen and thorax. It 

 receives blood through lateral paired openings, 

 arranged segmentally, and drives it forwards by 

 rhythmical contractions. 



FiQ. 38. — Periplaneta Americana. The male dissected from the right 

 side. The testes, which are very small in the adult, are not figured, 

 (c. H. H.) 



A, anus. AN", antennary lobe of supra-oesopbageal ganglion, with anten- 

 nary neiTe cub sbort. C, crop. CG-, supra-oesopbageal ganglion. OL, colon. 

 CK, anal cercus. CX, coxa. E, elytron. F, femur. eGr, frontal ganglion. 

 IFN", visceral nerve. G-, gizzard. G-P, one of tbe gonapophyses. GJ- 5, fiftb 

 abdominal ganglion. H, hepatic caecum. HT, heart. I, ileum. L, lingua. 

 LIT, nerve to labrum. LP, labial palp, M, musbroom-sbaped gland. 

 MO, Malpigbian C£eca opening into junction of mesenteron and ileum : tbey 

 are much longer and more numerous than indicated. ]VLD, ejaculatory duct. 

 ME, mesenteron. MIT, maxillary nerve. MP, maxillary palp. PIT, labial 

 nerve. PP, podical plate, diagrammatically drawn. R, rectum. S, sub-ceso- 

 phageal ganglion. SD, salivary duct just above its opening into the mouth. 

 SG-, salivary glands. SL, style borne by ninth sternum. SB. salivary 

 receptacle. ST, one of the abdominal stigmata. T, proximal joint of the 

 tarsus. TB, tibia. TR, trochanter. T 5, first thoracic tergum, or pronotum. 

 T3, third thoracic tergum', or metanotum. VGr, visceral ganglion. "W", wing. 

 2, tergum of second abdominal segment. 8, tergum of eighth abdominal 

 segment. 



M 



