THE CIRRIPEDIA. 



475 



species, with a short flattened peduncle, with calcareous scales), 

 and depressed. The larva has a shell in the form of a carapace, 

 which is cut short or truncated in front, where it has a horn on 

 each side. The under surface of the larva is flat and broad, and 

 is formed of thinner membrane than the back or dorsal surface. 

 The horns just alluded to are long in the larva of Lcpas anatifcra, 

 and short in the species Scalpellwn, now being described, and 

 their ends are either rounded and excessively transparent, or 

 furnished in other kinds with an abrupt minute sharp point. 



\-\'^\KOv Scalpelliim vu'gare{hom\>€[o\\.) larva, second stage. (After Darwin.) 



Mr. Darwin saw distinctly a long thread-shaped organ bear- 

 ing excessively fine hairs in lines so exactly like the long plumose 

 spines on the antennse of the larva of the last stage (and by 

 Avhich the mature Balamis adheres to surfaces) that he had not 

 the least doubt that these horns were the cores in which antennae 

 were in process of formation. Behind these horns, and near each 

 other on the lower surface (sternal) of the body, there are two 

 other minute doubly curved horns, and within each of them 

 there is a most delicate and jointed thread-shaped structure on 

 a thicker base. There are thus at first two sets of antennae in 

 the larva. Anterior to the points of origin of the smaller antennae 

 is seated a heart-shaped eye, but in some species this eye is not 

 perfectly developed when they are born. There are three pairs of 

 limbs seated close together ; each leg of the first pair always con- 



