SQUID. 105 



mantle arterv already noticed, and the lateral mantle 



*j \j 



arteries which follow the postcavse. On either side the 

 heart receives a branchial vein, coming from the gill ; while 

 in front it gives off an anterior aorta which runs forward. 



Look on the side of the gill nearest the mantle and see 

 the branchial artery. Trace it towards the middle line 

 and find the branchial heart, just behind the branchial 

 vein. This receives the blood from the postcava already 

 noticed, and also from a precava which comes from in 

 front through the kidnev, but is not so easilv traced. 



/ / */ 



Sketch all parts of the circulatory apparatus which you 

 have seen. 



The course of the circulation may be briefly described 

 as follows : The blood is forced to all parts of the body by 

 the systemic heart. After supplying these regions it 

 collects in the pre- and postcavae and is brought to the 

 branchial hearts, which pump it through the branchial 

 arteries to the gills. From the gills it returns to the 

 systemic heart by way of the branchial vein to repeat its 

 circuit. 



Carefully trace the intestine backwards from the vent, 

 removing the systemic heart and the remains of the kid- 

 neys. Just behind the level of the systemic heart it will 

 be found to enter the thick-walled, muscular stomach. 

 This stomach gives off, behind, a large, thin- walled blind 

 sac, which extends far back into the body mass. Close to 

 where the intestine leaves the stomach the oesophagus 

 enters it. Trace the oesophagus forward to the region of 

 the neck, but not farther at present. In its course it can 

 be followed through the liver. Sketch the alimentary 

 tract as if viewed from the side, inserting intestine, ink- 

 sac, stomach, blind sac, liver, and oesophagus, leaving 

 room for the anterior end of the latter to be inserted later. 



