58 FIRST LESSONS IN ZOOLOGY. 



lifted up, and then the "mantle" taken up with it can be 

 carefully, and without injuring the clam, pressed away 

 from the shell, and allowed to fall down over the exposed 

 side of the clam in its former, natural position. The up- 

 per valve, thus partly removed, can be now pulled away from 

 the other by tearing apart the ligament which holds it to 

 its fellow- valve. 



Now we can obtain some idea, without further injuring 

 or materially displacing the parts of the body of the clam. 

 In the first place, we see that the creature has no head ; 

 what is commonly called the "head" or "neck" because it 

 projects out of the shell, sometimes to a distance greater 

 than the length of the whole shell, is a double tube, rather 

 sensitive to the touch and very extensible, like india-rub- 

 ber. This is called the "siphon" (Fig. 60, si). On look- 

 ing at the black end we see that there are two openings, 

 surrounded by a fringe of finger-like feelers or "tentacles." 

 The lower opening allows the sea-water laden with the 

 clam's food, i.e., animalcules, perhaps even young clams 

 when too small to be seen with the naked eye, and other 

 young swimming sea-animals, to pass into the interior of 

 the body. After entering the body, a current of sea-water, 

 thus teeming with life, enters the mouth. 



To see where the mouth is, and the foot and gills as well 

 as other parts, we shall have to lift up a thin fleshy veil 

 which conceals them. This veil is a part of the fleshy walls 

 of the body, called the "mantle." It is very thick and 

 muscular at the edge of the shell. 



Upon removing the thin mantle from over the body, we 

 see the gills, These are broad wrinkled sheets, two on 

 each side of the animal, which are free at the edge, hang- 

 ing down like a double curtain on each side of the body, 

 when the animal is held with its dorsal side uppermost. 



In front of the gills, i.e., towards the front part of the 

 shell, are two pairs of delicate lappets (Fig. GO, p], which are 

 called feelers. Now, the mouth is a small irregular open- 

 ing, situated between and at the base of these feelers, or 



