BARNACLES. 199 



tions. The under-surface of the body is also muck 

 corrugated 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 

 attained. 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, tow T ards 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 Ento- 

 mostracous* Crustacean, or Water-flea, but removed to 

 another tribe. It represents, in fact, a Ci/pris/f 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 antenna', which project from the shell. The 



* From two Greek words — iprofior (entomos), cat up, and oarpaKov 

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

 with minute bodies very much divided and inclosed in a shellv 

 covering. 



+ See figure on p. 181. 



