GENUS CORONULA. 411 



into the six sutures ; in C. diadema they send similar pro- 

 longations into the sutures, and fill up, as 1 believe, the six 

 chambers (PL 16, fig. 7, v) lying between the radii and alae : 

 I have examined only one specimen of C. diadema in spirits, 

 and this had the ovarian tubes in an early state of develop- 

 ment, when they can with difficulty be distinguished from 

 the pulpy corium ; the orange-coloured masses, however, 

 which rilled the six cavities, resembled the layer which cer- 

 tainly consisted of undeveloped ovarian tubes and caeca, 

 lying over the basal membrane. The ova are wonderfully 

 numerous ; their length is ^ths of an inch. The larvae 

 have been noticed in the anatomical introduction. 



BrancJdcB. — These are immensely developed, covering 

 almost four fifths of the area of each side of the sack. 

 Each consists of two nearly equal folds, attached verti- 

 cally to the carinal end of the sack, and transversely across 

 the upper end extending to the animal's body. The outline 

 of the free part is rounded. Both folds of both branchiae 

 are deeply plicated on both sides ; hence the superficies of 

 the whole is very great. We shall find that this structure 

 is common to the three following allied genera, but with 

 these exceptions, I have observed double branchiae only in 

 one species of one other genus, namely, in Chthamalus 

 dentatus. 



Attachment. — The shells adhere with remarkable strength 

 to the whale's skin. Having, until recently, examined 

 only separated specimens, and observing portions of the 

 whale's skin adhering to the outside, and solidly filling up the 

 cavities on the under side, I did not doubt that the shell 

 had the power of forming, by its own action, a deep cavity 

 in the skin of the whale. Inspection of the basal outline of 

 the walls of the shell (PI. 16, fig. 5) of C. balanaris, will 

 show how singularly unfitted its structure is for any bur- 

 rowing process ; and I was led to speculate on the possi- 

 bility of the pupa being able to bury itself deeply in the 

 skin, but rejected this view as opposed to what is known 

 of the habits and structure of the pupae of other Cirripedes. 

 Having now examined several specimens of C. diadema 

 adhering, in a group, to a large piece of skin, in Mr. 

 Stutchbury's collection, it has become evident that the 



