112 BALANID.E. 



must have some home-logical signification ; here then we 

 have at least an appearance of the abortion of appendages ; 

 whereas, at the posterior end of the cephalo- thorax, no such 

 appearance is presented. Moreover this interspace of mem- 

 brane is divided nearly in the middle by a most conspicuous 

 fold, which, on the view here adopted, would mark the sepa- 

 ration of the seventh (cephalic) from the eighth (thoracic) 

 segment ; and the interspace and fold are thus simply ex- 

 plained. Lastly, I have shown, in the Introduction (p. 18), 

 that the first and five succeeding pairs of cirri of the mature 

 Cirripede present certain small, but significant, resemblances 

 in structure and in the origin of their nerves, with the outer 

 pair of maxillipeds and with the five pairs of ambulatory 

 legs in the Podophthalmia ; which resemblances are all 

 futile, if the cirri belong to the 7th, 8th, 9th, 10th, 11th, 

 and 12th segments of the cephalo-thorax, or those imme- 

 diately succeeding the mouth ; but are full of meaning, if 

 the six pairs of cirri belong, as I believe, to the 9th, 10th, 

 11th, 12th, 13th, and 14th segments, or the six posterior 

 segments of the cephalo-thorax. 



Before commencing on details, I may premise that I have 

 examined the pupa of Lepas australis, pectinata, fasci- 

 cularis, and anatifera, of Conchoderma virgata, partially of 

 Dichelaspis Warwickii, of Ibla quadrivalvis, and of Alcippe 

 I amp as ; and in the Balanidee, of Balanus balanoides and 

 Hameri. In the pupae of all these genera there is a most 

 close general agreement in structure, excepting in minute 

 details : I was surprised to find exactly the same slight dif- 

 ferences in the spines on the first pair of natatory legs, as 

 compared with the succeeding pairs, in Balanus Hameri, 

 as in Lepas. The abdomen and caudal appendages of the 

 pupa in the abnormal Alcippe, as we shall presently see, 

 offer the only marked exception to this uniformity of cha- 

 racter throughout the Thoracica. The outline of the cara- 

 pace or shell is usually not so blunt at the anterior end, as in 

 the pupa of Lepas australis (PL 30, fig. 2) ; more commonly 

 the shape is that of the pupa of Alcippe (PL 23, fig. 16). 

 In Lepas pectinata the two posterior points of the carapace 

 are produced into two short spines. The surface of the 

 carapace in L. australis is lined, as represented in fig. 4 : 



