54 Invertebrate Zoology. 



the scalpel. Note the left mantle-lobe covering the whole 

 surface of the animal, except the muscles. Through the 

 semi-transparent mantle, the outlines of the underlying 

 viscera may be seen. 



Along the dorsal edge, midway between the muscles, por- 

 tions of the dark green liver, the cream-colored reproductive 

 gland, and the brownish Keber's organ are to be noted, in 

 the order named. Further posteriorly and dorsally, between 

 Keber's organ and the posterior adductor muscle, the heart 

 may be observed, lying in the delicate pericardial sac. If 

 the animal is still alive, the pulsations of the organ may be 

 noted. Immediately in front of the posterior adductor, and 

 lying somewhat lateral to the heart, the yellowish organ of 

 Bojanus is to be noted. 



The foot is a plough-shaped organ, pointed at its anterior 

 end, and supported from the lower margin of the great, 

 swollen, soft-bodied visceral mass. 



With a pair of scissors remove the left lobe of the mantle, 

 cutting around the anterior and posterior adductors. The 

 visceral mass nearly fills up the cavity between the two mantle- 

 folds (mantle or pallial chdmber) and is crossed on each side, 

 diagonally, by two fringe-like gills. If the gills are followed 

 anteriorly, they will be found to end near two small gill- like 

 organs which lie just posterior to the anterior adductor. 

 These organs, of which there are two on each side, are the 

 palps. They lie, one pair above, and one pair below, the 

 mouth-opening. 



Examine the siphonal region. The mantle will here be 

 found to be specialized in such a way as to form two pro- 

 trusible tubes, of which the lower leads from without into 

 the mantle chamber. 



Make a drawing of the above-mentioned organs. 



