136 



THE FOOD OF ANIMALS 



pound eyes and very long feelers (antennae), which are able to 

 explore a considerable area in the neighbourhood of their owner. 

 And, as might be expected in a scavenging animal, organs of 

 smell are well developed, being here in the form of tufts of deli- 

 cate flattened hairs attached to the small feelers (antennules), 

 which are placed in front of the large ones. It is no doubt 

 largely by the sense of smell that lobsters (and crabs) find their 



'^'^^ 



Fig. 402. — Gastric Mill of Crayfish (enlarged) 



A, Stomach in section. B, Parts of mill dissected out. oe^ Gullet; Tjk, chewing region; hk, straining region; 

 kl, fold between two parts of stomach; md, intestine; op, front bar of mill; so, side-bar; sz, bar carrying 

 lateral tooth; mz, bar carrying middle tooth. 



way to the traps baited with offal that are set for them. These 

 animals possess efficient means for dealing with the food when 

 once this is secured, for there are no less than six pairs of jaws 

 constituted by the specialization of limbs, and working from side 

 to side in the usual arthropod manner. Nor is this all, for the 

 Lobster, like many other crustaceans, is provided with a compli- 

 cated chewing apparatus in the stomach, known as the gastric mill 

 (see fig. 402), and consisting of a framework of hard parts which 

 bear three tooth-like projections, one long ridged tooth on either 

 side, and a forked median tooth borne on a downwardly-directed bar. 

 By means of appropriate muscles attached to the framework the 

 three teeth can be brought together so as to effectually crush 

 anything that happens to be between them. The hinder part 

 of the stomach is specialized into a straining apparatus, numerous 

 stiff bristles projecting into its cavity and interlacing with one 

 another so as to constitute a very efficient sieve. Such parts of 

 the food as cannot be reduced to fine particles by the action of 

 the jaws and gastric mill are ejected to the exterior through the 

 mouth. The internal chewing arrangements remind one strongly 



