DIGESTIVE SYSTEM 



SI) 



80. Food and Food-getting. — The food of the crayfish is 

 both plant and animal, living and dead. One of the simple 

 water plants, Chara (ka/ra), furnishes the crayfish with 

 lime for its skeletons. Shells of snails and their own 

 shed skins also help to supply lime. Crayfish seize food 

 with their pinchers and move it towards the mouth. Small 

 food particles are also carried towards the mouth by cur- 

 rents of water produced by the mouth parts and the ab- 

 dominal appendages. Particles of food are torn loose by 

 the teeth or mandibles. 



81. Digestive System. — The mouth is just back of the 

 teeth, and connects with the stomach by a short esophagus. 



Figure 86. — Organs of Crayfish. 



The stomach is divided into front and back parts. The 

 front part possesses a grinding structure known as the 

 gastric mill, which serves to shred and crush the food and 

 make it ready for digestion in the back part. The liver. 

 or digestive gland, pours a fluid into the stomach, which 

 prepares the food for absorption by the walls of the stom- 

 ach and intestines. The intestine begins at the back end 

 of the stomach and extends to the last segment. 



