198 EVENINGS AT THE MICROSCOPE. 



Yes, here are more. These are evidently in their second 

 stage. There is an increase in length ; for whereas the 

 former was only -nj^th of an inch in length, these have 

 attained to a length of -^th of an inch. Yet this increase 

 is observable in no other dimension than that of total 

 length, and this is due to the development of the terminal 

 spine of the shield, which is now much produced, and cut 

 into minute teeth. The anal fork is also attenuated, 

 lengthened, and bent abruptly downward at the base, 

 where it is very mobile ; another bend in the middle 

 throwing the extremity into the horizontal again. The 

 delicately membranous pouch-like proboscis is more clearly 

 seen beneath the breast, the extremity of which is directed 

 backwards. In front of this organ there are two decurved 

 very mobile bristles, set on pedicles, or stalks, the whole 

 closely resembling the internal antennae in the higher 

 Crustacea. The lateral horns or external antennae appear 

 to terminate in a very delicate brush of hairs, which does 

 not seem to be capable of being protruded. 



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 occa- 

 sionally resting on sea-weeds and Diatomacea, 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 these 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 downwards ; 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 



