CRAWFISH 7.5 



IV. INTERNAL ORGANS 



CIRCULATORY SYSTEM 



1. With scissors cut away the dorsal surface of the carapace, 

 by two cuts which extend from the hind margin forward toward 

 the eyes, and connect anteriorly by a transverse cut. Do not in- 

 jure the underlying parts when removing the cut part of the 

 carapace. 



2. Remove the delicate skin along the median line and ex- 

 pose the pericardial sinus. This cavity receives the arterial blood 

 from the gills. 



3. The heart, which lies within the pericardial sinus, is a 

 thick walled muscular organ. It receives the blood from the 

 sinus by three pairs of valvular apertures, the ostia. 



4. What is the function of the circulatory system? Notes 

 required. 



5. Five vessels pass anteriorily from the heart. The median 

 one is the opthalmic artery. On either side of this is an anten- 

 nary artery, and from the broadest part of the heart are given 

 off the hepatic arteries. Posteriorly from the heart runs the 

 dorsal abdominal artery from which the sternal artery passes to 

 the ventral surface of the body. This is an open circulatory 

 system because in the tissues of the body the blood leaves the 

 capillaries and finds its way back to the heart by way of a series 

 of spaces called the sinuses. 



6. Draw side view of heart and main branches of circula- 

 tory system. 



REPRODUCTIVE ORGANS 



THE FEMALE 



I. The ovary lies below the pericardial sinus, and frequently 

 contains conspicuous eggs. There are two anterior lobes and a 

 median posterior lobe. 



