662 



THE BARNACLE. 



either set directly upon it, as the common acorn barnacle, so plentiful 

 on our coasts, placed upon a footstalk of variable length, as in the 

 ordinary goose mussel, or even sunk into the supporting substance, as 

 is the case with the whale barnacles. When young the Cirrhipedes 

 are free and able to swim about, and are of a shape so totally different 

 from that which they afterward assume that they would not be recog- 

 nized except by a practised eye. 



Along the under surface are set six pairs of limbs, not furnished with 

 claws, but being developed at their extremities into two long filaments, 

 joined and covered with hairs. By means of these modified limbs 

 the Cirrhipedes obtain their food. The common acorn barnacle of 

 our coasts affords a familiar and beautiful example of the mode by 

 which this structure is made subservient to procuring a supply of food. 

 The closed valves at the upper part of the shell are seen to open slight- 

 ly, a kind of fairy-like hand is thrust out, the fingers expanded, a 

 grasp made at the water, and the closed member then withdrawn into 

 the shell. 



This hand-like object is in fact the aggregated mass of legs with 

 their filaments. As the limbs are thrust forward they spread, so as to 

 form a kind of casting-net, and as they return to the shell they bring 

 with them all the minute organisms which were swimming in the 

 water. This movement continues without cessation as lono; as the 

 barnacles are covered with water, and appears to be as mechanically 

 performed as the action of breathing is performed by the higher 

 animals. 



The common Goose Mussel, or Duck Barnacle, is so called on 

 account of the absurd idea which was once so widely entertained, that 

 this species of barnacle was the preliminary state of the barnacle goose, 

 the cirrhi representing the plumage, and the valves doing duty for the 

 wings. 



This Barnacle is tolerably universal in its tastes. It clings to any- 

 thing, whether still or moving, and is the 

 pest of ships on account of the perti- 

 nacity with which it adheres to their 

 planks. Its growth is marvellously 

 rapid, and in a very short time a ves- 

 sel will have the whole of the sub- 

 merged surface coated so thickly with 

 these Cirrhipedes that her rate of speed 

 is sadly diminished by the friction of 

 their loose bodies against the water. 



A good example of these creatures is 

 afforded by the well-known Acorn Bar- 

 nacles, so plentiful on our coasts. They have no necks like those of 



The Acorn Barnacle {Bala- 

 nus balanoides). 



