V 



MOLLUSCS: THE MOLLUSCS 241 



are the labial palpi, and it is by their action that food- 

 particles which have been brought in with the water are 

 conveyed to the mouth. Note at the posterior part of 

 each mantle-lobe a fringed portion which, together with 

 a corresponding part on the other side, forms the inhalant 

 sipJion. The cilia of the fringes carry water and food- 

 particles into the space enclosed by the mantle- lobes; 

 this space is the mantle-cavity. After the food has been 

 taken o^it and the water has passed through the finely 

 striated gills it is collected in a common cavity which 

 extends above the two sets of gills on each side. This 

 space is called the supra-branchial cavity. This cavity 

 is continuous posteriorly with a space between the right 

 and left mantle-lobes, which is connected with the 

 exterior by an opening above the inhalant siphon called 

 the exlialant sip/ion. The function of the gills is partly 

 to produce currents of water carrying the food to the 

 mouth, and partly respiratory^ The mantle is an impor- 

 tant organ of respiration. / 



Make a drawing showing the organs described ^TT^ 



TECHNICAL NOTE. Carefully cut away the mantle and gills 

 from the leftside, and also the labial palpi, being careful not to dis- 

 turb the visceral mass. 



Note two openings along the line where the gills and 

 foot come together. The uppermost is the opening of the 

 ureter giving exit to the excretion from the kidneys; the 

 lower is the opening of the duct frofn the reproductive 

 organs and is called the genital aperture. The products 

 from both of these organs are carried out through the 

 exhalant siphon^ 



Note that th* mouth leads by a short tube (oesophagus 

 or gullet) into a large cavity, the stomach, which is sur- 

 rounded by a greenish mass, the digestive gland. 



TECHNICAL NOTE. Carefully cut the delicate covering of the 

 dorsal portion of the visceral mass and expose a cavity. 



