METAMORPHOSES OF CIRRIPEDES. 119 



surprising that the disc should have been edged with cement, 

 and that a tube, similarly formed, should have grown out 

 of the ultimate segment : it shows, I presume, that the 

 cement-tissue will grow out, whether or no the pupa has 

 succeeded in finding a proper object for attachment. Lastly, 

 I have felt some surprise, in two or three instances in ob- 

 serving some dark purple pigment-cells, like those in the 

 corium, within the terminal tube of cement ; and likewise 

 within the spokes of cement in the disc : this is the only fact 

 which causes me the least doubt, whether I have rightly de- 

 termined the nature of the terminal tube, as whollv formed of 

 cement tissue; or whether it may not be covered by an outer 

 integument, itself lined by true corium, coloured purple. 



Finally, I may add, that, excepting in small details, the 

 prehensile antennas present no difference throughout the 

 Order : I have minutely examined them in several genera of 

 the Lepadidae ; and in the Balanidse, I have seen them in Co- 

 ronula, and in several species of Balanus. In B, halanoides 

 I have examined them carefully; they are smaller and thicker 

 than in Lepas, with the second or main segment bowed 

 outwards, carrying its usual single spine ; with the disc 

 excised on its inner margin and apparently without the 

 spoke-like vessels for the cement ; and with the ultimate 

 segment proportionably longer, and carrying, I believe, six 

 spines, of which two appeared to be longer and more 

 flexible than the other four shorter and somewhat hooked 

 spines. In Coronala balanaris, also, the terminal segment 

 is, proportionably to the others, of large size. Not only 

 throughout the order, but throughout the whole Class, the 

 antennae are singularly uniform in structure, as will be seen, 

 when the last two orders are described. 



Byes. — These present no difference, except in size, 

 throughout the class ; and have been sufficiently described 

 in my former volume. The true basal segments of the an- 

 tennae (incorrectly designated formerly as sternal plates or 

 segments) are separated from each other by a deep fold ; 

 and are separated from the edges of the carapace on each 

 side by a crest and slight fold (PL 30, fig. 7, c ; and 4) ; 

 these folds and crests die out posteriorly, and disappear. 

 The hinder, rounded margins of the basal segments are 



