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. 



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