COMMON COCKROACH. 295 



PLATE VIII. 



COMMON COCKROACH (Periplancta orientalis), FEMALE, 



Dissected so as to show its digestive, nervous, and reproductive apparatus ; the ' fat body,' and 

 a considerable portion of the dorsal integument having been removed. 



OF the external organs are seen the multi-articulate antennae, the 

 segmented anal appendages or * cerci/ the compound eyes, portions of the 

 epicranium, of the terga, of the pro-, meso-, and meta-thorax, and of the eight 

 terga of the abdominal somites ; and finally, the three pairs of legs arti- 

 culated to the thoracic somites, and consisting each of a proximal segment 

 known as the coxa ; a second and much smaller segment, distinct in these, 

 though not in the saltatorial Orthoptera^ from the coxa, and known as the 

 trochanter ; a third, the femur, beset below with spines ; a fourth, the tibia, 

 more richly armed with spines than the femur ; and the fifth, the tarsus , 

 which is quinque-articulate. 



a. Antennae consisting of three elongated basal segments, and a multi- 



articulate appendage made up of as many as ninety-two joints. 



b. i, #. 2, b. 3. Tibiae, sub-quadrangular in shape, and beset along their 



two narrower sides with spines. 



c. ( Cerci anales,' consisting of twelve segments, the terminal one conical, 



the others thickly beset with hairs. As sexual characters may be 

 noted the absence of the sub-anal styles possessed by the male, and 

 the median emargination of the supra-anal dorsal plate with which 

 the cerci articulate. The cerci perhaps represent a pair of abdominal 

 limbs. They are commonly found in Orthoptera, Pseudo-Neuroptera, 

 and all Thysanura. 



d. Nerve ganglion developed upon the nervus recurrens, and seen to give 



off a nerve on either side, which passes backwards upon the crop to 

 the gizzard and has itself fusiform dilatations of a ganglionic character 

 developed upon it. 



e. Common duct communicating with the two lobes of the dendritic salivary 



gland. The ducts of the two salivary glands fuse mesially with each 

 other, In the angle formed by the convergence and fusion of the ducts 

 of the two salivary bladders or reservoirs with which they fuse in 

 turn, so that the compound duct finds an outlet into the mouth 

 by means of a short common canal. The figure does not accurately 



