lOO ARTHROPODS 



be careful that the dehcate organs on the dorsal side may 

 not be molested. 



(2) This exposes the heart, an oblong, whitish body 

 surrounded by a membrane, the pericardial sinus. This sac 

 receives the blood from the gills after it has been mixed 

 with oxygen. Carefully remove the sinus and expose the 

 heart. Look for holes on its upper surface and for small, 

 white tubes running from it toward the head. There are 

 two lioles in the top of the heart, tivo beneath, and one on 

 each side. These are guarded by liplike valves on the inside, 

 so that when the heart contracts, the blood is driven out 

 through the arteries to the various parts of the body. The 

 blood on leaving the arteries moves out into the viscera of 

 the body and is finally collected in irregular reservoirs which 

 communicate with the gills. The path of the blood is from 

 the body to the gills, from the gills to the heart, and from the 

 heart to the body. Draw heart (X2). 



(3) The principal arteries that may be found are as fol- 

 lows : Superior abdominal artery which passes back from 

 the heart, resting on the reproductive organs and the mus- 

 cles. Study it carefully and make out the different branches. 

 The sternal artery branches off from this near the heart. 

 The ophthalmie artery runs from the middle of the ventricle 

 anteriorly passing over the stomach. Find branches run- 

 ning to the stomach and head. The antennary arteries 

 arise near the antero-lateral angles of the heart. These sup- 

 ply the antennae, the green gland and the lateral walls of 

 the stomach. Make a drawing showing the dorsal view 

 of the circulatory system. Through the wall of the ventral 

 side of the abdomen may be seen the inferior abdominal 

 artery. Cut away the wall of the abdomen and follow the 



