BARNACLES. 199 



marked with longitudinal lines which resemble corruga- 

 tions. The under-surface of the body is also much cor- 

 rugated transversely. 



In the first moult the spine of the shield was greatly 

 increased, the size of the body itself remaining stationary ; 

 in the second moult the ratio is reversed, the body has 

 largely increased, but the spine is nearly unchanged. 



We cannot follow the metamorphosis any farther by 

 personal observations ; but from the researches of others, 

 and especially of Mr. Darwin, we know that other stages 

 have to be passed before the final fixed condition is at- 

 tained. As yet no perceptible advance has been made, by 

 either of the two moultings which we have traced, from 

 the free, jerking, dancing Water-flea that was first hatched, 

 towards the sessile Barnacle inclosed in its shelly cone of 

 several valves, and firmly fixed to the solid rock ; and we 

 are yet at a loss to imagine how such a change can be 

 effected. 



Nor is the matter apparently helped by the next moult ; 

 for though there now ensues a great change of form, it 

 does not seem to resemble the adult Barnacle much (if at 

 all) more than before. If described without reference to 

 its parentage, it would still be considered an Entomostra- 

 cous* Crustacean, or Water-flea, but removed to another 

 tribe. It represents, in fact, a Cypris ; \ the body with its 

 fringed limbs being now included within two convex valves, 

 like those of a mussel or other bivalve shell, either united 

 by a hinge along the back, or rather soldered together 

 there, so as only to allow a slight opening and closing, by 

 the elasticity of their substance. The fore part of the 

 head is now greatly enlarged, as are also the antennae, 



* From two Greek words evropos (entomos), cut up, and 

 (ostrakon), a shell. A term applied to a group of the Crustaceans 

 with minute bodies very much divided and inclosed in a shelly 

 covering. 



t See figure on p. 181. 



