314 



MOLLUSCA 



[CH. 



of a muscle running into the stalk, and by the contraction of this, 

 when the cup is applied to any object, a partial vacuum is produced. 

 By means of the suckers the Squid can take a firm hold of its prey. 

 The hind-foot is the tube known as the funnel (Figs. 143' and 

 146). The posterior end of this is overlapped by the hind end of 

 the mantle ; in other words, it projects into the mantle-cavity. The 

 mantle is very muscular; by the contraction of longitudinal 

 muscles running towards the apex of the hump the mantle-cavity is 

 widened ; by the contraction of circular muscles it is narrowed, and 

 by the alternate action of these two sets of muscles, water is sucked 

 in and forced out of the mantle-cavity. 



FIG. 144. A diagram showing the relation of the kidneys to the pericardium 



in Sepia. 



1. External opening of the kidney into mantle-cavity. 2. Internal opening 

 of the kidney into the pericardial coelom. 3. Opening of the right kidney 

 into the dorsal sac and hence into the left kidney. 4. Left kidney, 



ventral portion. 5. Keno-pericardial canal. 6. Pericardium (part of 



the coelom). 7. Branchial heart. 8. Dorsal sac common to both kidneys. 



A. Arrow passing into left kidney by external opening from mantle-cavity. 



B. Arrow passing into right kidney through external opening into median 

 lobe. ' c. Arrow passing into external opening and then into internal 

 opening, and so into pericardial coelom. The extension of the coelom in 

 which the generative cells arise is not shown in this diagram. 



When, however, the mantle-cavity is contracted, two projecting 

 pegs on the inner side of the mantle fit into sockets on the outer 

 side of the funnel (6 and 8, Fig. 143). No water can then escape 

 over the free edge of the mantle, and all is ejected in a narrow and 

 forcible stream through the funnel. The funnel itself is muscular 



