554 



Marvels of the Universe 



than its own swimming po^^•e^s \\ithin reach of its food. It therefore chooses a convenient spot and 

 attaches itself by its antennas. These, the reader will remember, were in the Cypris stage converted 

 into tubes with sucking discs. With these the Cypris fixes itself, and through the hollow channel 

 pours the cement. This hardens gradually into a stout membrane which forms the tube of the 

 adult Barnacle. AU this time the structure inside the two-parted shell has been altering. The organs 

 have, as it were, turned round. With the succeeding moults the bluish-white shells, which are the 

 most conspicuous part of the creature, have been forming, and when the Barnacle finally rids itself 

 of Cypris nature it has become such an object as is seen in the two photographs on page 553. Of 

 the six pairs of legs, each one has developed into two jointed branches bearing beautiful plumes, 

 like fringes, which are constantly in motion, curving outwards and inwards, so that the Barnacle 

 can at will spread out a fan of twenty-four dehcate fronds, or retract them by curling them inwards, 

 until they can be packed away in the snowy sheU. 



" But," says one, " this is a shell, not a crab," and certainly outward appearances do justify 



Photo by] 



A BIG ACORK BARNACLE. 



These large specimens of Harrier's Barnacle were attached to the bottom of a ship. The trap-doors are missing, but they 

 are much like those of the common species that encrusts the rocks, as shown in another photo. (Natural size.) 



the remark ; but it is the hfe-history of the Barnacle which has influenced the judgment of the 

 expert. No moUusc passes through the three stages just described, while crabs do ; besides, the 

 internal structure of the animal is crab-like, and if we regard the shell as a horny covering, the 

 similarity is stiU more distinct. Turn it round so that the mouth occupies a similar position to that of 

 the crab, and the whole creature falls into proper order. The mouth has complex j aws, the branched 

 antennae, " kicking the food into the month," take the place of legs (and giUs), while to complete the 

 resemblance, the Barnacle at times casts off some of its covering (including the curled feet), just 

 as the crabs throw off not only their coat of mail, but their inner linings as well. In one particular 

 point, however, the Barnacle is a law to itself ; it never discards the curious shields which compose 

 its shell ; but as it grows, it adds rim after rim to every part, and by this means enlarges its covering 

 to meet its increasing needs. 



These shelly shields demand a moment's notice. The parts of which they are composed are 

 of such odd shapes : some are triangular, others have one straight edge and one curved, and some 

 near the edge have one side raised high and gradually sloped away on the other till they reach the 

 level of the remaining sections. Again, their number and the variety of shapes appear to differ 



