142 MORPHOLOGY OF INVERTEBRATE TYPES 



22. Remove left half of endophragmal skeleton by cutting the 

 sternites and endosternites in the median line. Remove left wall 

 of the cephalic portion of the cephalothorax and left half of the 

 abdominal tergites and pleurae to the pleopods. Gradually 

 remove all muscles of the left half of the body in the thoracic 

 region and abdomen by lifting them and cutting at their at- 

 tachment places with scissors, and by carefully separating them 

 from the injected blood-vessels. Do not touch any muscles or 

 organs in the cephalic region. When the dissection is accom- 

 plished, the cephalic region will show only such structures as 

 lie immediately under the carapace, while the thoracic region 

 and abdomen will show all organs of the left half of the body ex- 

 cept the removed muscles. Immediately behind the cervical 

 groove will be seen the heart which gives off anteriorly a median 

 blood-vessel the anterior aorta (or cephalic artery) and posteriorly 

 the posterior aorta (or dorsal abdominal artery); the blood- 

 vessel running parallel with the lateral cervical groove to the 

 second antenna is the left antennal artery. The heavy vessel 

 running behind the heart down to the ventral side is the single 

 sternal artery. It ends in a median longitudinal ventral vessel 

 the forward part of which is called the anterior ventral or thoracic 

 artery and the hind part the posterior or ventral abdominal artery. 

 Immediately behind the left eye will be seen the left procephalic 

 lobe with the anterior gastric muscle attached by the other end 

 to the large stomach. The stomach is partly concealed by a 

 heavy muscle the adductor of the left mandible behind which 

 the posterior gastric muscle attached to the stomach and cervical 

 groove is visible. Under the anterior end of the antennal artery 

 is the flexor of the second antenna. Under the antennal artery, 

 occupying all the space between heart and endoskeleton and 

 extending all the way to the abdomen, is the left lobe of the 

 liver. Underneath the latter are the cut edges of the endoster- 

 nites which form the roof of the sternal canal. Inside that sternal 

 canal is the nervous chain and beneath this the ventral artery 

 which has been already mentioned. Extending longitudinally 



