230 EVENINGS AT THE MICKOSCOPE. 



terminal hook ; while its posterior side is set with 

 strong vibrating cilia. The anal fork is greatly in- 

 creased in dimensions, has its edges armed with spines 

 articulated to its surface, and is marked with longi- 

 tudinal lines which resemble corrugations. The under- 

 surface of the body is also much corrugated trans- 

 versely. 



In the first moult the spine of the shield was greatly 

 increased, the size of the body itself remaining station- 

 ary ; in the seond moult the ratio is reversed, the body 

 has largely increased, but the spine is nearly in statu 

 quo. 



"We cannot follow the metamorphosis any farther 

 by personal observation, 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 appreciable 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 Bar- 

 nacle 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 ef- 

 fected. 



l^or 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 with- 

 out reference to its parentage, it would still be con- 

 sidered an Entomostracous Crustacean, or Water-flea, 

 but removed to another Tribe. It represents, in fact, a 

 Oypris ; * the body with its fringed limbs being now 

 * See figure on page 209. 



