62 LEPADID.E. 



moulted ; but the surface gradually disintegrates and is 

 removed, perhaps sometimes in flakes, whilst new and 

 larger layers are formed beneath. In Scalpellum, I as- 

 certained that the new membrane, connecting together the 

 newly-formed calcified rims under the valves of the capi- 

 tulnm, was formed as a fold, with the articulated spines 

 which it bears, all adpressed in certain definite directions. 

 This fold of new membrane, when the old membrane 

 splits and yields, of course expands, and thus the size of 

 the capitulum is increased. In the peduncle, lines of 

 splitting can seldom be perceived, except, indeed, in the 

 sub-globular, embedded, downward-growing peduncle of 

 Anelasma, as described under that genus. I do not 

 understand what determines the complicated lines of 

 splitting of the old membrane between the several valves 

 of the capitulum, — without it be simply, that along these 

 lines alone, the old membrane is not strengthened by the 

 new membrane being closely applied under it, the new 

 being formed, as we have just said, in a fold, in order to 

 allow of increase in size. Although, as I believe, there is 

 strictly no exuviation in the outer membranes of mature 

 Lepadidoe, it seems that narrow strips of membrane are 

 cast off from between the valves, for the few first moults, 

 after the final metamorphosis of the larva. I may here 

 remark that, in most sessile Cirripecles, the outside mem- 

 brane connecting the operculum and shell, is regularly 

 moulted. 



The delicate tunic lining the sack, (a mere duplicative 

 of that thick one, forming the outside of the capitulum, 

 and generally transformed into valves,) and the integuments 

 of the whole body, are regularly moulted. With these 

 integuments, the membrane lining the oesophagus, the 

 rectum, and the deep olfactory pouches, and the horny 

 apodemes of the maxillae, are all cast together. I have 

 seen a specimen of Lepas, in which, from some morbid 

 adhesion, the old membrane lining one of the olfactory 

 pouches had not been moulted, but remained projecting 

 from the orifice as a brown shrivelled scroll. The new 



