CRA YFISH. 



end of the body, so that the antennules and antennae lie far 

 in front of it. The fore-gut, which is lined by a chitinous 

 cuticle, includes a short "gullet," on the walls of which there 

 are small glands, hypothetically called "salivary," and a 

 capacious gizzard, which is distinctly divided into two 

 regions. 



In the anterior (cardiac) region there is a complex mill ; in the 

 posterior (pyloric) region there is a sieve of numerous hairs. The mill 



FIG. 144. Longitudinal section of lobster, showing some 

 of the organs. 



H. t Heart; AO., ophthalmic artery; aa., antennary artery; aA.. 

 hepatic artery ; ST., sternal artery ; SA., superior abdominal 

 artery ; MG. t mid-gut ; DG. t digestive gland ; HG., hind-gut ; 

 Ex.) extensor muscles of the tail; Fl., flexor muscles of the tail; 

 I A ., inferior abdominal artery; G., gizzard ; C.. cerebral ganglia 

 />., pericardium ; 7" 1 ., testes. 



is very complex ; there are supporting c ' ossicles " on the walls with 

 external muscles attached to them, and internally projecting teeth which 

 clash together and grind the food. Three of the teeth are conspicuous ; 

 a median dorsal tooth is brought into contact with two large laterals. 

 On each side of the anterior part of the gizzard there are two limy 

 discs or gastroliths, which are broken up before moulting, and though 

 quite inadequate to supply sufficient carbonate of lime for the new 

 skeleton, seem to have some relation to this process. The occurrence 

 of chitinous cuticle, setae, teeth, and gastroliths in the gizzard, is 

 intelligible when the origin of the fore-gut is remembered, and so is the 

 dismantled state of this region when moulting occurs. 



The mid-gut is very short, but outgrowths from it form 



