BLATTA. 227 
The cavity of the gizzard is continued into that of the 
mesenteron, a comparatively short tube which leads into a 
still shorter and narrower intestine, terminating in a 
vesicular vectum. At the front end of the mesenteron are 
eight (or nine) hepatic ceca or hollow glandular processes, 
and at its hind end are six tufts of extremely fine long 
processes, called the malpighian tubules. They constitute 
the excretory organs of the cockroach. The rectum has six 
longitudinal folds. As in the lobster, the mesenteron alone 
is formed from endoderm, and absorption is confined to it. 
The parts in front and behind are formed of ectoderm and 
are lined by chitin. The digestive fluid from the ceca 
is said to pass forwards into the crop where it is mixed 
with the food. Here the food is digested or reduced to 
a soluble condition. The gizzard then relaxes and allows 
the digested food to pass on into the mesenteron, in 
which absorption is effected. The most important dif 
ferences in the alimentary system from that of the lobster 
are (1) the presence of salivary glands (connected with the 
terrestrial habit); (2) the division of the “stomach” into a 
large storage crop and a small gizzard ; and (3) the presence 
of excretory organs opening into the alimentary canal. 
The cockroach has a complex system of muscles. In 
the abdomen the dorsal and ventral abdominal muscles are 
little modified. They serve to execute the 
respiratory movements, not to flex the abdomen. 
In the thorax the muscles are broken up into special limb 
muscles, moving the legs and wing-muscles for flight. The 
alary muscles run as a triangular band from the tergon of 
each segment towards the heart, spreading out under the 
pericardial septum and meeting its fellow below the heart. 
They may serve to move the pericardial septum. 
As in the lobster, the muscles are attached to the exo- 
skeleton but there is no endophragmal skeleton. The cavity 
of the body is largely filled up by the corpus adiposum or 
fat body, a mass of fat cells. 
Bined: The heart is a long delicate tube running in 
the median dorsal line of the thorax and abdo- 
men. It lies just under the terga. In each 
segment (three thoracic and ten abdominal) it opens by 
paired valves or ostia into the pericardial cavity surround- 
Muscular. 
Vascular, 
