224 ELEMENTARY BIOLOGY. [CHAP. 



exception of the ambulatory appendage bearing the 

 genital orifice ; leave that in situ] and remove the 

 skeleton together with its related muscles, being careful 

 not to injure the digestive or reproductive organs. 



Cut along the dorsal middle line of the cephalic 

 skeleton, and continue the incision downwards, clear 

 of the green-gland. Remove the hard parts, but leave 

 the adductor muscle of the mandible in situ. Dissect 

 away any extraneous tissue and wash carefully. 



a. The superior abdominal artery ; a backward con- 

 tinuation of the heart, immediately above the 

 intestine. It distributes branches metamerically 

 to the intestine (hind-gut) and adjacent parts. 



b. The ophthalmic artery; a similar forward continua- 

 tion of the anterior end of the heart. It runs over 

 the stomach and distributes branches to the eye 

 stalks and parts immediately adjacent. 



t. The hepatic artery. Turn the exposed digestive 

 gland downwards ; branches of the above vessel 

 will be seen ramifying in it. Cut its main trunk 

 across and remove the gland, noting the branches 

 to the mid-gut ; the main trunk can now be traced 

 beneath the genital gland, to its origin, from the 

 antero-ventral region of the heart. 



d. The sternal artery ; a large trunk, arising from the 

 heart at the base of a. It runs vertically down- 

 wards towards the ventral surface, passing to one 

 side of the intestine, and perforating the nervous 

 system (obvious as a delicate greyish median-ven- 

 tral cord. Cf. Sect. J.). It subdivides into 

 a. The antero-ventral artery ; a median trunk, ex- 

 tending forwards to the mouth region, and dis- 



