LIGIA. qT 
invagination, and their anterior ends attached to the 
hypodermis of the middle of the preceding segment. In 
the lateral, and also the epimeral regions, the body cavity 
is almost entirely filled up with the muscles moving the 
appendages; these muscles are attached to the dorsal 
side of the animal in these regions (lev.m.). The 
longitudinal muscles of the ventral side (v./.m.) have 
their attachments similar to those of the dorsal side. 
The joints of the thoracic appendages, like the appendages 
themselves, are provided with extensor and flexor muscles. 
The mandibles are provided with a powerful set of 
muscles, attached to the dorsal side. The proximal ends 
of the remaining mouth appendages have thickened 
skeletal rods, forming an internal framework, to which the 
muscles moving them are attached. 
Tur DIGESTIVE SYSTEM. 
The digestive system consists of the alimentary canal 
and -its glands—the salivary glands, and the hepato- 
pancreas or digestive gland. 
The alimentary canal can be divided into four parts — 
the oesophagus, the stomach, mid-gut and rectum. 
The oesophagus (PI. II., fig. 15 oes.) opens by a slit-like 
aperture surrounded by the mouth appendages. Its course 
is almost vertical, and it opens into the anterior end of the 
stomach on the ventral side. The oesophagus receives the 
secretions of the salivary glands. 
The stomach forms an efficient mill for triturating 
the miscellaneous substances upon which the animal feeds. 
It lies in the cephalic and first thoracic segments. The 
wall of the stomach, which is composed of columnar cells, 
is lined with chitin, and is folded in a complicated 
manner; thus a number of chitinous lamellae are formed, 
