_Metamorphoses._--I will here briefly describe the Metamorphoses, as far as known, common to all Cirripedia, but more especially in relation to the present family. I may premise, that since Vaughan Thompson’s capital discovery of the larvæ in the last stage of development in Balanus, much has been done on this subject: this same author subsequently published[4] in the ‘Philosophical Transactions,’ an account of the larvæ of Lepas and Conchoderma (Cineras) in the first stage; and seeing how totally distinct they were from the larva of the latter stage in Balanus, he erroneously attributed the difference to the difference in the two families, instead of to the stage of development. Burmeister[5] first showed, and the discovery is an important one, that in Lepas the larvæ pass through two totally different stages. This has subsequently been proved by implication to be the case in Balanus, by Goodsir,[6] who has given excellent drawings 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and drawings of the larvæ of five species in this same early stage, and has most kindly permitted me to quote from his unpublished paper[7]. I am enabled to confirm and generalise these observations, in all the Cirripedes in the Order containing the Balanidæ and Lepadidæ. [4] Philosophical Transactions, 1835, p. 355, Pl. vi. [5] Beiträge zur Naturgeschichte der Rankenfüsser, 1834. Mr. J. E. Gray, however, briefly described, in 1833, (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. [6] Edinburgh New Philosophical Journal, July 1843, Pls. iii and iv. [7] This will appear in the October number (1851) of the ‘Annals of Natural History.’