246 



ANIMAL BIOLOGY. 



[Part II. 



and Fig. 77, A. It lies in the pericardial sinus, being suspended 

 therein by fibrous bands, the alse. Six main valvular aper- 

 tures admit the blood from the pericardial sinus, two dorsal (75, 

 d. v.), two ventral, and two lateral (77, A., /. v.). The blood 



A. 



FIG. 77. CRAYFISH HEART : CIRCULATION : GREEN GLAND. 

 A. Heart from left side. B. Diagram of Circulation in the Thorax. 



C. Green Gland. 



a. v. Afferent vessel to gill. an. a. Antennary artery. 6. c. v. Branchio- 

 cardiac vein. c. p. Conical process at base of antenna, d. v. Dorsal valve of 

 heart, e. v. Efferent vessel from gill. gr. gl Excretory part of green gland. 

 he. a. Hepatic artery. I. v. Lateral valve of heart, op. a. Ophthalmic artery. 

 p. s. Pericardial sinus, s. a. a. Superior abdominal artery, s. Saccular part 

 of green gland, s. s. Sternal sinus, st. a. Sternal artery. 



leaves the heart by seven arteries, the positions of which are 

 seen in the side view of the heart (77, A.). The median anterior 

 ophthalmic artery (op. a.) runs forward over the stomach, to 

 supply the eyes and region adjacent. On either side of this are 

 the antennary arteries (an. a.) which supply the stomach, man- 

 dibular muscles, green gland, and antennary appendages. Two 

 hepatic arteries (he. a.) are mainly distributed to the liver. 

 These five start from the anterior end of the heart. From the 

 posterior end the superior abdominal (s. a. a.) runs back along 

 the intestine, supplying it and the dorsal part of the abdomen. 

 A sternal artery (st. a.) runs downwards and slightly forwards, 

 gives off branches to the vas deferens or oviduct, pierces the 



