32 A MANUAL OF ZOOLOGY 



end of the body. Make a drawing of the s pecimen asjt-. 

 now stands. -"^ ''- — — --"■ 



- A'5air of white granular 'bodies will be seen on either 



side of the intestine and extending posteriorly to about 

 the region of the he"art, renal or nephridial organs. Pick 

 these away carefully alter severing the mesentery, and 

 the heart will be plainly brought to yie''^. As the renal 

 organs are taken out the intestine may be followed 

 between the two cavities. 



The venae cavae are thin, -transparent vessels. The 

 anterior cava runs back as far as the branchial heart and 

 there unites with the . posterior cava which at this point 

 becomes nearly as broad as long. Sometimes these vessels 

 contain blood so they may be easily traced in preserved 

 ^specimens. Upon dissecting the posterior vena cava 

 away the dorsal mantle artery is seen. Notice the bran- 

 chial hearts are in separate pericardial chambers. Turn 

 these hearts over. How many vessels open into them, 

 and how many out of them? The blood is collected in the 

 branchial hearts from the vena cava and forced to the 

 gills, there collected again and brought to the systemic 

 heart. 



Lay the anterior end of the intestine back and find a 

 ^ pouch-sEaped sac below the ink bag, the spleen. This 

 receives a branch from the anterior vena cava. 



THE SYSTEMIC HEART AND ARTERIES^What 

 , is the shape of the heart? How situated? Size?. Is it 

 placed directly on the median line? Is it placed with 

 about equal portions on either side of the median line? 

 How many vessels lead to or from the heart? Find the 

 anterior, jand the posterior aorta. Also the right and the 

 left branchial veins. Trace tne ppsteriqr aorta and notice 

 the branches. The anterior aorta may be traced later to 

 the head. Make a dr awing of the circulatory system. 



THE DIQBSTIVE~St STEM— Cut a^ay the systemic 

 heart with its arteries also the, blind sac (a transparent 

 membrane which contains the stomach.) 



The stomach is a large muscylar bag. Trace from 

 the anterior, end the liiteetiiie and the oesophagus side by 

 side. Notice tijat the intestine takes a turn at this.poi^t_ 

 and terminates in the recjtum. Trace .the oesophagus until 



