64 Invertebrate Zoology. 



makes an abrupt turn downwards and forwards, and passes 

 towards the head. It soon enlarges and forms a secondary 

 heart which lies, as dissection will show, to the left of, upon 

 and to the right of, the oesophagus. Large branches are 

 given off to the muscles of the foot, siphon, and to the head. 



Make a drawing of the heart and principal blood-vessels. 



Cut the heart in two and reflect, exposing the pericardial 

 chamber. Note the serous lining, and especially the open- 

 ing which leads into the renal organ. This opening, which 

 is of considerable morphological significance, will be found 

 somewhat below and inside of the point of entrance of the 

 branchial and the renal veins, and near the deepest point of 

 the pericardial chamber. 



Make a drawing of the interior of the pericardium. 



(b) The Excretory System. The location of the glan- 

 dular and of the tubuliferous portions of the kidney have 

 already been noted. With a small pair of scissors cut along 

 their common line of union, opening the chamber of the 

 kidney. Observe the numerous parallel lines of tubules 

 which make up the substance of the lower, tubuliferous por- 

 tion. The larger, acinous portion of the kidney is made up 

 of large lobules over which blood-vessels ramify, on their 

 course from the upper part of the body to the gill. Look 

 for the large opening leading from the renal to the mantle 

 chamber, and also for the smaller opening which leads from 

 the pericardial chamber. 



Make a drawing of the glandular organs of the kidney. 

 Carefully remove the acinous portion of the renal organ. 



(c) The Reproductive System. If the specimen being 

 examined is a female, the ovary will be found as already 

 noted. Trace the oviduct as it leaves the lower inner side 



