Shell-fish industries . igure 13 represents the inner surface of the mantle(m) lining the left valve of the shell of the hard clam,Venus. All other parts of the body have been a few grains of powdered carmine or fine sand areallowed to settle through the water upon a living specimenprepared in this way, they may be seen to adhere to themantle wherever they touch it, and then, together withthe mass of mucus in which they are held, they begin tomove in the direction indicated by the arrows of thefigure. This movement is due to the action of cilia, lashingcontinually in definite direct
Shell-fish industries . igure 13 represents the inner surface of the mantle(m) lining the left valve of the shell of the hard clam,Venus. All other parts of the body have been a few grains of powdered carmine or fine sand areallowed to settle through the water upon a living specimenprepared in this way, they may be seen to adhere to themantle wherever they touch it, and then, together withthe mass of mucus in which they are held, they begin tomove in the direction indicated by the arrows of thefigure. This movement is due to the action of cilia, lashingcontinually in definite directions, and uncontrolled bythe nervous system. Everything is moved downward, Ciliary Mechanisms 57 finally reaching a sharply defined tract parallel with themantle edge. Here the stream is directed backward toa point just below the opening of the incurrent siphon(i s). It will be remembered that the siphon is a pairof tubes formed as a growth from the mantle, and that inthe living clam, a strong stream of water enters the. Fig. 13.—Ciliation of the mantle of the round clam or little neck(Venus mercenaria). The arrows indicate the directions takenby foreign particles in the mantle chamber that come in contactwith the mantle wall. The palps are represented at p. lower one. If a mass of material being moved by themantle cilia were brought in contact with this stream,it would be swept far back again into the mantle cham-ber, so it comes to rest in this small bay below the siphon,where a considerable quantity of it may collect. Whatis to become of it? It could not easily be carried di-rectly outward between the edges of the mantle, becausethe entire shell is covered in the bottom. The only 58 Our Food MoUusks path to the exterior is through the lower tube of thesiphon, and ciha could not possibly move the massagainst its powerful incoming current. When a sufficient quantity has collected, the clamsuddenly contracts the adductor muscles, the result beingthat some of the water filling
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Keywords: ., bookcentury1900, bookdecade1910, bookpublishernewyo, bookyear1910
