BAKNACLE8. 229 



Bcjond stage. There is an increase in length ; for 

 whereas the former was only t| o^h of an inch in length, 

 these have attained to a length of ^Vth of an inch. 

 Yet this increase is observable in no other dimension 

 than that of total length, and this is due to the devel- 

 opment 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 mo- 

 bile ; another bend in the middle throwing the extrem- 

 ity into the horizontal again. The delicately mem- 

 branous pouch-like j)roboscis is more -clearly seen be- 

 neath the breast, the extremity of which is directed 

 backwards. In front of this organ there are two de- 

 curved very mobile bristles, set on pedicles, the whole 

 closely resembling the internal antenna? in the higher 

 Crustacea. Tlie lateral horns or external antennae 

 appear to terminate 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 sec 

 them now occasionally resting on sea-weeds and Diato- 

 inacecB, 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 afibrds 

 us an opportunity of tracing the Barnacle to another 

 point of its transformations. Tlie 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 



