THE " CRABS'-EYES.' 



29 



middle region of that part of the carapace which lies 

 behind the cervical groove ; or, in other words, in the 

 dorsal region of the thorax. In front of it, and tlierefore 

 in the head, is a large rounded sac, the stomach (fig. 5, 

 cs ; fig. 6, cs, 2)s), from which a very delicate intestine 

 (figs. 5 and 6, hg) passes straight back through the thorax 

 and abdomen to the vent (fig. 6, a). 



Fig. 6. — Asfacvsjfvfiafilis. — A longitudinal vertical section of the ali- 

 mentary canal, with the outline of the body (nat. size) : — a, vent ; a//, 

 anterior gastric muscle ; b(/, entrance of left bile duct ; c</, cervical 

 groove ; CCS, cfficum ; ejn; cardio-pyloric valve ; es, cardiac portion 

 of stomach ; the circular area immediately below the end of the 

 line from cs marks the position of the gastrolith of the left 

 side ; /if/, hind-gut; lb, labrum ; If, lateral tooth of stomach : 

 m, mouth ; ?iifj, mid-gut ; 7iif, median tooth ; «?, oesoiihagus ; jm', pro- 

 cephalic process ; ^p.*/, posterior gastric muscle ; px, pyloric portion of 

 stomach ; r, annular ridge, marking the commencement of the 

 hind-gut. 



In summer, there are commonly to be found at the sides 



of the stomach two lenticular calcr i*eous masses, which 



are known as " crabs'-eyes," or gastroliths, and were, in 



old times, valued in medicine as sovereign remedies for all 



sorts of disorders. These bodies (fig. 7) are smooth and 



flattened, or concave, on the side which is turned towards 

 3 



