488 THE BARNACLES. 
by a curious shield, composed of two parts, the junction taking place across the centre of 
the body. Though perfectly harmless, these creatures can be made very offensive, for the 
natives of Moluecca are accustomed to use the long sharp tail spine as the head for an arrow 
or lance, and thus make a most formidable weapon. Many of these crustacea attain the 
length of two feet, so that the spike is nearly a foot in length, and is capable of inflicting a 
deadly wound. 
The edges of the hinder portion of the shield are deeply toothed, and the space between 
the teeth is occupied by a rather long and sharply-pointed spine, which is not fixed, but is 
movable on its basis. The feet are mostly furnished with tolerably strong claws. 
The Molucea Crabs often leave the sea and crawl upon the sand, where they may be 
taken without much difficulty. They cannot endure the heat of the sun’s rays, and are 
in the habit of burrowing into the sand when the sunbeams beat too fiercely on their shells. 
Sometimes they do not bury themselves very deeply, and then they are discovered by the 
projecting tail-spike, which shows itself above the level of the sand, and betrays the position 
of the animal. As they pass over the sand they present a very curious appearance, as their 
large shield-like shell entirely covers the limbs, and the creatures seem to be carried along 
by some external agency rather than to be propelled on their own limbs. Owing to the 
shortness of the legs, and the large rounded shell, the Molueca Crabs are almost helpless 
if laid on their backs, being obliged to wait until some friendly wave may strike them and 
enable them to resume their proper attitude. These crustaceans occur largely Im certain 
strata, and are found in a fossil state, many species attaining to a very great size. One 
living species (Limulus cyclops) is a native of the Kast Indies, and goes by the popular 
name of PAN-FISH, or SAUCEPAN-CRAB, because the shell, when the limbs and body have 
been removed and the tail spine permitted to retain its place, has some resemblance to the 
useful culinary article from which it derives its name. Jt is often used as a ladle for dipping 
water out of a vessel. 
BARNACL E'S; (CiR RIPE DITA. 
WE now come to the last members of the crustacea, creatures which were for a long time 
placed among the mollusks, and whose true position has only been discovered in comparatively 
later years. Populariy they are called Barnacles, but are known .to naturalists under the 
general term cirripedes, on account of the cirri, or bristles, with which their strangely 
transformed feet are fringed. 
When adult, all the cirripedes are affixed to some substance, being either set directly 
upon it, as the common acorn-barnacle, so plentiful on European coasts; placed upon a foot- 
stall 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 cirripedes are free and 
able to swim about, and are of a shape so totally different to that which they afterwards 
assume, that they would not be recognized except by a practised eye. More will be said 
on this subject. 
Along the under surface are set six pairs of limbs not furnished with claws, but being 
deveioped at their extremities into two long filaments, jointed and covered with hairs. By 
means of these modified limbs the cirripedes obtain their food. The common acorn-barnacle 
affords a familiar and beautiful example of the mode by which this structure is made sub- 
servient to procuring a supply of food. The closed valves at the upper part of the shell are 
seen to open slightly, 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 long 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. 
