THE COCKROACH 175 



should be removed from all the segments, care being taken not 

 to cut deeply, for the internal organs lie close to the surface. The 

 mouth leads by a narrow gullet into a large pear-shaped crop, on 

 whose sides are two pairs of white salivary glands, each embracing 

 a thin-walled receptacle. The saliva produced by these glands 

 is conveyed forwards to the mouth by fine tubes which unite 

 before discharging. While in the crop considerable changes are 

 effected in the food by the action of the saliva and of the juices 

 produced by the " liver " tubes, whose secretion passes forward 

 into the crop. Immediately behind the crop is a small but firm 

 and muscular gizzard. Within this organ are six large horny 

 teeth, by which the food is finely crushed after leaving the crop ; 

 behind and between the teeth are numerous short bristles, which 

 serve as strainers to prevent any but very minute particles from 

 passing into the mid-gut. Close to the junction of the mid-gut 

 with the gizzard are about seven blind, club-shaped tubes 

 the " liver " tubes, which both discharge a digestive fluid upon 

 the food and also absorb the digested material and pass it into 

 the blood. The mid-gut is succeeded by the intestine, whose 

 commencement is marked by the attachment of numerous white 

 thread-like tubes of excretory function. The intestine is rather 

 closely coiled, and eventually passes into the rectum, which opens 

 to the exterior at the anus, and which is provided with six longi- 

 tudinal ridges the better to grasp and mould the faecal residues 

 to be expelled from the body. 



The eggs of the cockroach are laid in batches of sixteen at a 

 time, each batch being enclosed in a large, dark mahogany coloured 

 capsule somewhat resembling a small bean-seed. This structure 

 is formed in the peculiarly modified ventral plate of the 7th 

 segment, to which allusion has already been made. The eggs 

 pass into it singly from the right and left ovaries alternately, and 

 are placed upright in two parallel rows facing each other. Female 

 cockroaches may often be seen with the egg-case protruding from 

 the posterior end of the body, for they thus carry it about until 

 they have found a suitable nook in which to deposit it. When 

 the young are ready to emerge they push asunder the sides of 

 the capsule, which are cemented together dorsally so as to pro- 

 duce a longitudinal ridge, and escape through the slit thus opened. 



