Notwithstanding their agreement in this important peculiarity, the Nauplii of these two orders present material differences in many other particulars. The abdomen of the young Cirripede is produced beneath the anus into a long tail-like appendage which is furcate at the extremity, and over the anus there is a second long, spine-like process; the abdomen in the Rhizocephala terminates in two short points,—in a “moveable caudal fork, as in the Rotatoria,” (O. Schmidt). The young Cirripedes have a mouth, stomach, intestine, and anus, and their two posterior pairs of limbs are beset with multifarious teeth, setæ, and hooks, which certainly assist in the inception of nourishment. All this is wanting in the young Rhizocephala. The Nauplii of the Cirripedia have to undergo several moults whilst in that form; the Nauplii of the Rhizocephala, being astomatous, cannot of course live long as Nauplii, and in the course of only a few days they become transformed into equally astomatous “pupæ,” as Darwin calls them. The carapace folds itself together, so that the little animal acquires the aspect of a bivalve shell, the foremost limbs become transformed into very peculiar adherent feet (“prehensile antennæ,” Darwin), and the two following pairs are cast off; like the frontal horns. On the abdomen six pairs of powerful biramose natatory feet with long setæ have been formed beneath the Nauplius-skin, and behind these are two short, setigerous caudal appendages (Fig. 58). The pupæ of the Cirripedia (Fig. 57), which are likewise astomatous, agree completely in all these parts with those of the Rhizocephala, even to the minutest details of the segmentation and bristling of the natatory feet;[6] they are especially distinguished from them by the possession of a pair of composite eyes. Sometimes also traces of the frontal horns seem to persist.[7] As the Cirripedia and Rhizocephala now in general resemble each other far more than in their Nauplius-state, this is also the case with the individual members of each of the two orders.