. Concerning evolution. Evolution. FIGURE NO. 20 ADAPTATIONS IN BARNACLE Fig. I shows three ordinary ship-barnacles, Lepas anatina, at- tached to a floating log. They are crustaceans, free-swimming as larvae, which become adapted to sedentary life. The young forms fix themselves by the front part of the head, which grows out into a long flexible stalk (ST). From between the valves of an external shell of five pieces, something like an unopened pea blossom, six pairs of curled limbs (L) are protruded, which waft the micro- scopic food into the mouth. Fig. II shows the floating barnacle, Lepas f
. Concerning evolution. Evolution. FIGURE NO. 20 ADAPTATIONS IN BARNACLE Fig. I shows three ordinary ship-barnacles, Lepas anatina, at- tached to a floating log. They are crustaceans, free-swimming as larvae, which become adapted to sedentary life. The young forms fix themselves by the front part of the head, which grows out into a long flexible stalk (ST). From between the valves of an external shell of five pieces, something like an unopened pea blossom, six pairs of curled limbs (L) are protruded, which waft the micro- scopic food into the mouth. Fig. II shows the floating barnacle, Lepas fascicularis, attached to a detached piece of seaweed (S), which its growing weight is dragging below the surface. But the barnacle has secreted a gelati- nous buoy (B) with entangled gas, and this enables it to continue floating although its body (A) has become too heavy for the sea- weed. This is an interesting physiological adaptation. It should also be noted that the shell pieces are very lightly built. 138. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Thomson, J. Arthur (John Arthur), 1861-1933; Dwight Harrington Terry Foundation. New Haven, Yale University Press; [etc. , etc. ]
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Keywords: ., bookauthorthomsonjarthurjohnart, bookcentury1900, bookdecade1920
