282 



THE ANATOMY OF INVERTEBRATED ANIMALS. 



attached by six ligaments, corresponding with the alse of the 

 heart in insects, but not, like them, muscular. Except by 



lb 



Fig. 74.— Astacus, Longitudinal Section.— I, II, III, Sterna of first, second, and third 

 somites; a, oesophagus ; Id, labrum : I, metastoma ; G, membranous part of the 

 stomach; c, cardiac ossicle; pt. pterocardiac ; uc, urocardiac; cl, lateral cardiac; 

 p, cardio-pyloric valve ; pi., inferior pyloric valvular apparatus; m, anterior gastric 

 muscle ; m*, insertion of posterior gastric muscles; pc, procephalic processes; 

 h f , opening of hepatic duct ; v, pyloric csecum ; i, k, intestine ; gn, testis ; gn', gu ff , 

 vas deferens ; C, heart ; ao, ophthalmic artery ; aa, antennary ; ah, hepatic ; as, 

 sternal; ap, superior abdominal artery ; b, cerebral ganglia ; sg, azygos visceral 

 nerve. 



these ligaments, and by the arteries, which pass through it, 

 the walls of the pericardial cavity, or blood sinus (for such it 



