NATURAL HISTORY. 



fcide-marks, is covered, with their heard, white shells tightly closed with 

 their folding-doors, when the tide is out; but when the water covers them, 



the scene changes. Each individual barnacle opens 

 wide his ivory doors and extends a delicate feathery 

 hand, which keeps constantly beckoning all small 

 objects to enter and accept his hospitality. Alas 

 for them that come. His invitation reminds one 

 of the celebrated spider and fly. His constantly 

 moving hand is creating currents in the water, and 

 these bear him oxygen and food. When danger 

 birnacies {BcSus laia- threatens, he withdraws into his shell and shuts 



it up, and it is a considerable time before he ven- 

 tures out again, and then, at first, in a most cautious and suspicious 



manner. 



In our northern seas, in deeper water, other acorn-barnacles are found 

 much larger than this familiar form, but it is in the tropics that they 

 acquire their greatest development. One form occurring on the coasts of 

 Chili is nine or ten inches long and three or four in diameter. As may be 

 seen, such an example would furnish a considerable amount of flesh, and 

 the natives consume them to a large extent as food. Other species which 

 occur in other parts of the world are also eaten ; but none reach such a size 

 as this South American form. Others of the allies of the acorn-barnacles 

 live a semi-parasitic life, their choice of a habitat being often very interest- 

 im:. Thus one species is only found on the large sea-tortoise which fur- 

 nishes the tortoise-shell of commerce, while others are only found imbedded 

 in tlic skin of whales, and still others on the branches of the sea-fan corals. 

 These forms are not true parasites ; they do not feed on their hosts, but 

 take their food from the water just as do their more common relatives 

 which whiten the rocks along our coast. 



The barnacles with the fleshy peduncle are not so common in our seas as 

 are the aeorn-barnacles. The general appearance of themost common form 

 in the wanner seas is well shown in our cut. The barnacles are represented 

 as hanging down from a bit of floating pumice-stone, and from the lower 

 ones the leathery arms are represented as protruding from the valves in the 

 position they occupy when drawing water and food to the mouth inside 

 the shell. Some of these forms may reach a length of sixteen inches. One 

 species of stalked barnacle which is comparatively abundant along the 

 New England coasts, and which is frequently thrown up on the beaches 

 after a smnn. has the power of secreting a bladder-like float for itself, and 

 thus is independent of foreign support. 



Possibly barnacles are best known from their relations to navigation. 



