114 BALANID.E. 



to be the acoustic vesicle. These orifices occur in the 

 carapace, either in the same position, or a little more poste- 

 riorly, in the pupae of all Cirripedes. In Balanus balanoides 

 they are minute, being only ^th in diameter, but are 

 surrounded with a border : in Conchoderma virgata they 

 are also surrounded by a border : in Lcpas pectinata, 

 the orifices are ^gth of an inch in diameter, and are very 

 singular from being seated on rounded prominences, 

 causing the carapace to have two short, blunt horns in 

 front. In Lepas australis, and I believe in the other 

 species, the corium round the acoustic orifices is darkly 

 coloured ; and these coloured marks can be distinguished for 

 some little time on the peduncle of the young Cirripede, 

 after the metamorphosis, and after the entire organ, together 

 with the whole pupal carapace and eyes, has been moulted. 

 Knowing the connection in the higher Crustacea, of the 

 acoustic organs and the antennas, and seeing the very 

 backward position (figs. 2 and 4) of the one great pair of 

 antennae, I have always imagined that these orifices probably 

 marked the normal position of the anterior pair of antennae, 

 which, since the earlier larval stages, have disappeared. 

 And I now find* that Schodler affirms, that in most, if not 

 in all Daplmidae, there is a black spot in front of the eye, 

 which is connected with an opening in the basal portion 

 of the anterior antennae, and he concludes that it is an organ 

 of hearing. 



Antenna. — These, from their present position, and from 

 standing, in their earlier stages whilst within their en- 

 velopes or horns, exteriorly to the small medial pair (since 

 aborted), I believe to be the second pair; and this is 

 Mr. Dana's opinion. In my former description of these 

 very singular and important organs (PI. 30, figs. 4 and 8), 

 I have fallen into some considerable mistakes : the two 

 plates or segments (fig. 4, n), of which the posterior 

 margins are inflected as apodemes (n), carrying the eyes, 

 are certainly, as may be clearly seen in the pupa of Alcippe, 

 PI. 23, fig. 10, and as affirmed by Purmeister,t the basal 



* Quoted by Dana, ' Crustacea of United States Exploring Expedition,' p. 1204. 



f ' Beitrage zur Naturgeschichte der Kankenfiisser,' p. 19. In tab. 1 of this 



work there ure good drawings of the general structure of the pupa of a species 



