Shell-fish industries . fall into the grooves(g), and are then carried to the base of the gill. Herethey go to a ciliated tract leading to the palps and Ciliary Mechanisms 65 mouth (;;/). This is thenormal food collecting pro-cess. But when much materialarrives on the gill, it notonly falls into the grooves,but adheres to the surfacesof the folds (/) as it seems tostimulate a copious secretionof mucus, and the wholemass, both in the groovesand on the folds, becomescontinuous. Now begins astruggle between opposingtracts. The material in thegrooves is pushed toward thebase and th
Shell-fish industries . fall into the grooves(g), and are then carried to the base of the gill. Herethey go to a ciliated tract leading to the palps and Ciliary Mechanisms 65 mouth (;;/). This is thenormal food collecting pro-cess. But when much materialarrives on the gill, it notonly falls into the grooves,but adheres to the surfacesof the folds (/) as it seems tostimulate a copious secretionof mucus, and the wholemass, both in the groovesand on the folds, becomescontinuous. Now begins astruggle between opposingtracts. The material in thegrooves is pushed toward thebase and that on the foldstoward the free edge of thegill, as at b. The tension onthe string of mucus becomesso great that finally—and in-variably—it is lifted up outof the grooves and all isborne to the edge of the gill(c). Now, too, the wholegill is responding to thestimulus of a large quantityof foreign matter on its sur-face, by writhing and sway-ing from side to side. If it is the inner gill thathas made this collection,. Fig. 16.—Three folds of thesurface of the gill of thescallop (Pecten irradians)to illustrate automatic actionof cilia in bearing smallquantities of material to themouth on the tract markedm, and large quantities awayfrom the mouth and to themantle wall from the edge ofthe gill. 66 Our Food Mollusks it transfers its mass to the outer, or casts it off intothe mantle chamber. The outer gill often touches themantle, the cilia of which relieve it of its burden andcarry it away. Thus the gills as well as the palps of Pecten rejectmaterial when it is too abundant, but the process in thiscase is purely automatic. The course taken by foreignmatter is determined by its volume, and so certainly thatthe experimenter is soon able, when allowing carmineparticles to settle on the gill, to predict which path theywill follow on reaching its surface. There are few known mechanical contrivances ofanimal bodies more wonderful than this self-operatingmechanism of the Pecten gill.
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Keywords: ., bookcentury1900, bookdecade1910, bookpublishernewyo, bookyear1910
