1:30 BALANlD.fi. 



integrates ; in the primordial valves, however, which stand 

 far separate from each other, this membrane is moulted ; 

 and immediately after the first moult, the first layer of shell 

 appears under and a little way beyond each primordial 

 valve; shelly matter likewise appears, at least in some cases, 

 between the cells of the hexagonal tissue. The young shelly 

 valves are connected together, at each successive moult, by 

 narrower strips of membrane, till, in the case of Lepas, the 

 valves when mature come to touch each other (Lepadidae, 

 PL 1, fig. 5). The primordial valves are often preserved 

 for a long time on the umbones, or centres of growth 

 of the five valves, on which they occur, in the same manner 

 as the larva-shell is sometimes preserved on the apex of 

 certain spiral molluscs. Had not Cirripedes gone through 

 so many and such complicated metamorphoses, this last 

 state, when furnished only with primordial valves and with 

 several internal organs only partially or not at all developed, 

 would have deserved to have ranked as a special stage, and 

 not as merely subordinate to the last or pupal condition. 



In the Balanidae, or sessile Cirripedes, the young animal, 

 immediately after the metamorphosis, or still better if dis- 

 sected out of the pupal carapace, as I succeeded in doing 

 with Balanus balanoides, may be said to be pedunculated ; 

 for it is attached by a little disc of cement closely sur- 

 rounding the antenna?, the rest of the membranous basis 

 forming an almost semi-globular, flexible peduncle. The 

 valves, at this the earliest period, are all membranous, and 

 do not overlap each other. In the Balaninae they do not 

 present the peculiar structure of the primordial valves of the 

 Lepadidae ; but in the Chthamalinae, in Chthamalus, I saw 

 traces of this structure. Calcareous valves are soon formed 

 under the membranous valves. The opercular valves, at 

 this early period, are much larger than the valves or com- 

 partments of the shell, which are only four in number, 

 for the carino-lateral compartments are not yet formed. 

 The compartments from the first are surprisingly strong, 

 and have their alae already formed and overlapped by the 

 adjoining compartments; but of the radii there is as yet no 

 trace. The four compartments form a narrow but nearly 

 circular hoop, which, from its relatively large diameter, 



