162 ARTHROPOD A. 



pericardium at the side. Find these openings if possible. Do 

 you understand how blood gets into the heart? 



2. Note, at the anterior end of the heart, the ophthalmic 

 artery and the two antennary arteries. Trace the former forward 

 to the rostrum, cut it on the stomach and turn it forward for 

 future study. Trace the antennary arteries to the mandibular 

 muscles and cut them near the heart. Press the front end of 

 the heart back and note the two small hepatic arteries. Each 

 branches immediately, one division passing between the gonads, 

 and the other laterally. 



3. Remove the muscles on one side of the heart and examine 

 it from the side, noting the great sternal artery extending down- 

 ward, and the smaller dorsal abdominal artery running back above 

 the intestine. Follow the latter through the abdomen. 



4. Cut all arteries and remove the heart. Trace the anten- 

 naries through the mandibular muscles, noting the branch to 

 the stomach. 



5. Remove the thoracic viscera as before, follow the circum- 

 esophageal connectives forward and identify the cerebral ganglia 

 in order not to destroy them. 



6. Follow one antennary artery to the green gland, antennary 

 muscle, eye muscle, etc. 



7. Follow the distribution of the ophthalmic artery. 



8. Remove the intestine and muscles of the abdomen, and find 

 and trace forward the ventral nerve chain. Notice the position 

 of the ganglia and the nerves that leave them and the connec- 

 tives. In the thorax the ventral nerve chain passes beneath a 

 system of chitinous plates {the endophragmal skeleton) and lies 

 in a cavity, the ventral blood sinus. Note the enlarged sub- 

 esophageal ganglion, the cross commissure just back of the esoph- 

 agus, the nerves to the mouth appendages, nerves from the 

 cerebral ganglia, and nerves from the other ganglia. What indi- 

 cation is there that the sub-esophageal ganglia represent more 

 than a single pair? 



Sketch the nervous system. 



9. The sternal artery passes through the ventral nerve chain 



