ALCIPPE LAMPAS. 535 



encroaches almost equally on the dorsal, lateral, and ventral 

 surfaces. But if we were to suppose the extreme anterior 

 point of the body to be rapidly developed, the surface of 

 attachment or basis, without it grew still more rapidly, 

 could not possibly reach the dorsal surface, and would, 

 consequently, be confined to the ventral or rostral surface. 

 I have not seen the young of the ordinary or female Alcippe 

 soon after its metamorphosis, but in the male the develop- 

 ment of the extreme anterior end of the body is extraordi- 

 narily rapid, and from analogy we may fairly conclude that 

 this is likewise the case with the female. Hence I believe 

 that the horny disc answers to the cemented down, lower end 

 of the peduncle, in other members of the Lepadidse, and to 

 the basis in the Balanidse, and that it is confined to the ven- 

 tral or rostral surface, owing to the anterior or lower end of 

 the body having been rapidly developed. To make all the 

 parts, internal and external, of Alcippe, correspond with 

 those of other cirripedes, the main circular part of the horny 

 disc must be turned up at nearly right angles to its present 

 position (the dorsal or carinal integuments, to the right- 

 hand in fig. 5, being shortened), and then we should have 

 a peduncle, certainly very short and broad, but holding its 

 proper relative position.* 



Sack and its Muscles. — I have already described the 

 curious phalanx of spines, the long fine hairs, and thickened 

 condition of the inner tunic of the sack along the sides of 

 the orifice. This inner tunic is a reflexion from that en- 

 veloping the body of the animal, in the usual manner, as 

 may be seen in the section (PI. 22, fig. 5). Between the ex- 

 ternal membrane and the inner tunic of the sack (<?), there 



* In the genus Lithotrya, as long as the animal continues to bore into the 

 rock, the calcareous discs by which it is attached in its cavity, stand, as in 

 Alcippe (PI. 8, fig. 2, 2 a, Darwin's ' Monograph on the Lepadidre'), parallel to 

 the longitudinal axis, but as soon as the animal ceases to bore, and the discs 

 become converted into a cup, they occupy a normal position at right auglcs to 

 the peduncle. According to Reinhardt, these discs, in Lithotrya, are situated 

 on the carinal or dorsal surface of the peduncle, at which statement I now feel 

 considerable surprise, as undoubtedly the pupa must first permanently attach 

 itself by its prehensile antennae on its ventral or rostral surface. In Anelasma 

 I failed to discover any cement or cement-ducts; but I am now strongly 

 inclined to believe, considering that the extreme lower or anterior end goes on 

 growing, that the surface of attachment will be found to occur, as in Alcippe, 

 on the rostral surface, a little way below the orifice. 



