A Cephalophorous Mollnsk. 63 



gland, occurs as a series of tranverse folds along the roof 

 of the mantle chamber. In the female the gland extends 

 between the gill and the nidamental gland. 



At the very apex of the mantle chamber a slit-like open- 

 ing will be found. This opening leads from the cavity of 

 the renal organ. 



Make a drawing that will illustrate the anatomy of the 

 mantle chamber. 



Internal Anatomy. The systems of organs may be 

 dissected in the following order : 



(a) The Circulatory System.- -Though it is well to 

 use a hypodermic syringe with some colored liquid for trac- 

 ing out the arteries and veins, the larger blood-vessels may 

 be located in the uninjected specimen. The branchial 

 vein, seen from without, is a transparent line running 

 along the lower side of the area which we know to be that 

 of the gill. It may be followed nearly to the pericardium, 

 where it unites with a renal vein that returns the blood 

 from the lower, tubuliferous portion of the renal organ. 

 The common vein empties into the auricle of the heart. 



With a pair of scissors carefully open the pericardial 

 chamber, and gently lift the heart from the cavity. The 

 auricle will appear as an anterior division, thin-walled and 

 collapsed. The ventricle, lying posteriorly, is much larger, 

 and is provided with strong muscular walls. From the ven- 

 tricle arise two arteries. These pass from its posterior 

 end and convey blood to all parts of the animal. The vis- 

 ceral artery passes upwards, through the substance of the 

 liver, giving off branches to the stomach and reproductive 

 gland. By the careful use of probes the visceral artery 

 is not difficult to trace. The aorta, the second artery, 



