22 LEPADIMJ. 



quite unlike any other membrane in the animal. These 

 valves, which I have called primordial valves, resemble 

 pretty closely in shape the valves of the mature animal ; 

 the fork of the carina, however, is indicated only by a 

 slight constriction above the lower end. After the 

 exuviation of the larval integuments, and when calcifi- 

 cation commences, the first layer of shell is deposited 

 under, and then round these primordial valves. The latter, 

 in well preserved old specimens, may often be detected 

 on the umbones of the scuta, terga, and carina, but not 

 on the umbones of any other valves. 



The mouth seems one of the earliest parts developed : 

 in the youngest larva dissected, I could make out at least 

 points corresponding with each organ ; and, at the period 

 when the young Cirripede could be dissected out of its 

 larval envelopes, their general details were quite plain. 

 The labrum, however, had not become bullate. The 

 mouth, as we have seen, is formed under the rudi- 

 mentary mouth of the larva, and at the same relative 

 spot occupied by the probosciformed mouth of the larva 

 in the second stage. Thus far, in the young Cirripede 

 and larva, there has been no great change in the relative 

 positions of the parts : the rudimentary eyes, however, of 

 the former are developed posteriorly to (or above, as ap- 

 plied to a Cirripede,) the cast-off compound eyes of the 

 larva ; but the position of the mouth, of the antennas, and 

 of the several coloured marks in the corium, prove to 

 demonstration, the correspondence in both of part to part. 

 The case is rather different with what follows. 



The Cirri are developed at first of considerable length, 

 so that the young animal may soon provide itself with 

 food ; in Lejpas australis they are of great length, the 

 sixth pair consisting of seventeen or eighteen obscure 

 segments. The extreme tips of the twenty-four rami 

 of the six pair of cirri, are formed within the twenty- 

 four, corresponding, little, bi-segmental rami of the six 

 pair of natatory legs ; but as the cirri are many times 

 longer than these legs, they occupy in a bundle the 



