METAMORPHOSES. 9 



the difference in the two families, instead of to the stage 

 of development. Burmeister* first showed, and the dis- 

 covery is an important one, that in Lepas the larvae pass 

 through two totally different stages. This has sub- 

 sequently been proved by implication to be the case in 

 Balanus, by Goodsir,f who has given excellent draw- 

 ings of the larva in the first stage ; and quite lately, 

 Mr. C. Spence Bate, of Swansea, has made other detailed 

 observations and drawings of the ' larvae of five species 

 in this same early stage, and has most kindly permitted 

 me to quote from his unpublished paper J. I am enabled 

 to confirm and generalise these observations, in all the 

 Cirripedes in the Order containing the Balanidae and 

 Lepadiclae. 



The ova, and consequently the larvae of the Lepadidae, 

 in the First Stage, whilst within the sack of the parent, 

 vary in length from *007 to "009 in Lepas, to '023 of an 

 inch in Scalpellum : my chief examination of these larvae 

 has been confined to those of Scalpellum vulgar -e; but I 

 saw them in all the other genera. The larva is somewhat 

 depressed, but nearly globular ; the carapace anteriorly is 

 truncated, with lateral horns ; the sternal surface is flat 

 and broad, and formed of thinner membrane than the 

 dorsal. The horns just alluded to are long in Lepas 

 and short in Scalpellum ; their ends are either rounded 

 and excessively transparent, or, as in Ibla, furnished with 

 an abrupt, minute, sharp point : within these horns, I 

 distinctly saw a long filiformed organ, bearing excessively 

 fine hairs in lines, so exactly like the long plumose spines 

 on the prehensile antennae of the larvae in the last stage ; 

 that I have not the least doubt, that these horns are the 

 cases in which antennae are in process of formation. Pos- 



* Beitrage zur Naturgeschichte der Rankenfusser, 1834. Mr. J. E. Gray, 

 however, briefly described, in lS33,(Proceedings, Zoological Society, October,) 

 the larva in the first stage of Balanus ; in this notice the anterior end of 

 the larva is described as the posterior. 



f Edinburgh New Philosophical Journal, July 1843, Pis. iii and iv. 



% This will appear in the October number (1851) of the 'Annals of 

 Natural History.' 



