BARNACLES 229 



in a very delicate brush of hairs, which does not seem to 

 be protrusile. 



The little animals in this state swim, generally, back 

 downward; though they frequently assume a perpendicular 

 position, both direct and reversed. I see them now oc- 

 casionally resting on sea-weeds and Diatomacece^ though 

 the limbs seem even worse fitted than before for crawling, 

 since the spines or bristles with which they are fringed 

 are much increased in length, especially on the third pair. 



A specimen nearly twice as large as this last affords us 

 an opportunity of tracing the Barnacle to another point 

 of its transformations. The modifications are chiefly in 

 the proboscis and the anal fork. The former now points 

 directly downward, is furnished with a pair of minute 

 spines on its anterior side, and with a terminal hook; 

 while its posterior side is set with strong vibrating cilia. 

 The anal fork is greatly increased in dimensions, has its 

 edges armed with spines articulated to its surface, and is 

 marked with longitudinal lines which resemble corruga- 

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

 gated 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 in statu quo. 



We cannot follow the metamorphosis any further 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 at- 

 tained. 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, 



