Sub-Class 1. Eiitomostraca. Order 7. Cirripedia. 205 



of Lepas, -which here are relatively small, and at this point there is a 

 narrow slit leading into the mantle-cavity. 



As for the appendages, the first pair of antennse is 

 present in a very rudimentary state ; in the Lepadidse it occurs on the 

 adhesive surface of the peduncle ; in the Balanidffi in a corresponding 

 position. A cement-gland opens on each antenna, and its 

 secretion serves for the attachment of the animal. The second 

 antennee, on the other hand, are wanting entirely in the adult. 

 There are usually three pairs of jaws, none of which are well- 

 developed. The ventral side of the body, which, as is evident from 

 Figs. 166, 167, is turned upwards, bears six pairs of cirri, each 

 consisting of a two-jointed shaft, with two multiarticulate, very- 

 flexible, whip-like rami; the outer is the exopod, the shaft and the 

 other branch, the endopod. The cirri, whose rami are fringed with 

 setae, can be extruded through the mantle-slit and withdrawn again ; 

 they serve to waft into the mantle-cavity the little organisms which 

 form the food of the animal, and when in motion the cirri stretch 

 through the slit close together, then widen out like a fan, come 

 together again, and are drawn back with a jerk. Among the 

 BalanidsB the anterior are considerably shorter than the posterior 

 cirri. The body is usually indistinctly segmented, and frequently 

 bears at its tip a pair of small jointed or unjointed caudal ap- 

 pendages. The adult has only a double nauplius-eye, whilst 

 lateral eyes are wanting. Heart and blood vessels are 

 ab sent. 



Tte ventral ganglion chain is much concentrated ; in the BalanidsB, 

 the ventral gangha are all united to a single large nerve mass. The digestive 

 tract terminates at the end of the body. Among the Lepadidse gills are 

 present in the form of thin-skinned whip-like appendages, springing from the 

 bases of one or more of the thoracic legs. These appendages, possibly- 

 representing the epipods, are -wanting in the Balanidse, -which are, howevei-, 

 provided -with a paii- of large folded gills arising -vrithin the mantle on either 

 side. In a degenerate state they are also present in the Lepadidss, -vrhere 

 they have a different function, -viz., that of carrying the ovigerous lamella 

 (see belo-w). 



In contrast to almost all other Crustacea, most of the Cirripedia 

 are hermaphrodite. Among the Lepadidae, the ovaries lie in 

 the peduncle, among the Balanidse on the adhesive surface ; an oviduct 

 opens on each side of the body; the branched testis is situate 

 in the body proper ; the seminal ducts open by a common aperture 

 on the tip of an elongate copulatory organ, posteriorly. It is 

 very curious that in certain Lepadidse, besides the hermaphrodite 

 individuals, very small males occur, attached to the former in the 

 mantle-cavity or at its opening. These complemental males* 



* In others an actual separation of sexes occurs ; the female possesses the usual 

 form, the males are pigmy, like the complemental males. 



