V. On the development of lepas fascicularis and the “archizoëa” of cirripedia

Abstract

Burmeister’s important discovery that in Lepas the larvæ pass through a Nauplius and a Cypris stage was made on the same Lepas which forms the subject of this paper. Burmeister, however, had evidently only a ball of this Lepas , some specimens of which were young in the Cypris stage, which had just settled; while others were dismissing young Nauplii , which, unless great care is taken, die very soon in captivity. He thus missed the intermediate stages, which, however, were at that time much less important, as the first thing that was wanted then was to establish the general outlines of the Cirriped development. The Nauplius of this Lepas has since been seen by Darwin, to whom Hancock showed it, “calling his attention to a proboscidiform projection on the underside of the larva of Lepas fascicularis when just escaped from the egg.” Neither J. v. Thompson’s nor Pagenstecher’s observations refer, as far as I can find out here, to Lepas fascicularis ; and it seems not to have been taken up again as an object for embryological researches until Claus published his paper on the Cypris -like larva (pupa) of the Cirripeds and its metamorphosis into the fixed animal (Marburg, 1869), a paper of which I have unfortunately only an abstract, as given by Nitsche in his embryological report for the year 1872, and by Claus himself in his ‘ Grundzϋge der Zoologie,’ which, however, affords nearly all the information necessary for my purpose. My object is to give an idea of the whole development of one Lepas as accurately as possible, which seems never yet to have been done, as our whole knowledge of the development of this group consists of fragments, collected mostly in the same way in which Burmeister gained his information.