BARNACLES AND ACORN SHELLS. l8l 



metamorphosis. When this is completed they are fixed for 

 life : their legs are now converted into prehensile organs ; they 

 again obtain a well- constructed mouth; but they have no 

 antennas, and their two eyes are now re-converted into a 

 minute, single, simple eye-spot. In this last and complete 

 state, Cirripedes may be considered as either more highly or 

 more lowly organized than they were in the larval condition. 

 But in some genera the larvae become developed into herma- 

 phrodites, having the ordinary structure, and into what I have 

 called complemental males ; and in the latter the development 

 has assuredly been retrograde, for the male is a mere sack, 

 which lives for a short time, and is destitute of mouth, 

 stomach, and every other organ of importance, excepting 

 those for reproduction." 



In this early condition these Cirripedes much resembled the 

 minute so-called water-fleas that swarm in our fresh-water 

 ponds and streams, and when upon the point of their last 

 change they laid their heads down upon the spot selected for 

 their future station in life. Then a natural marine glue, that 

 sets under water, exuded from their antennae, and they 

 became fixtures, head downwards. The two valves of their 

 old shells were thrown off, and the new ones, largely composed 

 of carbonate of lime, grew up from the base. 



Some of the Barnacles on our buoy are apparently dead, 

 and one of these we can take to pieces. Taking off one half 

 of the compound shell, we find the creature attached to the 

 floor of the chamber, evidently on its back. From the upper 

 end there arise the twelve limbs, six on each side, and each 

 one dividing into two branches, each branch a beautiful 

 feather with a wonderfully jointed, supple, purple-black stem, 

 closely fringed with purple hairs. It is from this plume-like 

 cluster of curling limbs that the order obtains its name (Latin, 

 cirrus, a curled lock of hair, and/^j, a foot = curl-footed). 



When the shell opens and the trunk which supports all 

 these limbs is thrust forward, each branch separates from its 



