Out of several Cirripedes, which are anomalous both in structure and development, _Cryptophialus minutus_ must be mentioned here; Darwin found it in great quantities together in the shell of _Concholepas peruviana_ on the Chonos Islands. The egg, which is at first elliptical, soon, according to Darwin, becomes broader at the anterior extremity, and acquires three club-shaped horns, one at each anterior angle and one behind; no internal parts can as yet be detected. Subsequently the posterior horn disappears, and the adherent feet may be recognised within the anterior ones. From this “egg-like larva”—(Darwin says of it, “I hardly know what to call it”)—the pupa is directly produced. Its carapace is but slightly compressed laterally and hairy, as in _Sacculina purpurea_; the adherent feet are of considerable size, and the natatory feet are wanting, as, in the adult animal, are the corresponding cirri. As I learn from Mr. Spence Bate, the Nauplius-stage appears to be overleaped and the larvæ to leave the egg in the pupa-form, in the case of a Rhizocephalon (_Peltogaster ?_) found by Dr. Powell in the Mauritius. I will conclude this general view with a few words upon the earliest processes in the development of the Crustacea. Until recently it was regarded as a general rule that, by the partial segmentation of the vitellus a germinal disc was formed, and in this, corresponding to the ventral surface of the embryo, a primitive band. We now know that in the Copepoda (Claus), in the Rhizocephala (Fig. 64), and, as I can add, in the Cirripedia (Figs. 61–63) the segmentation is complete, and the embryos are sketched out in their complete form without any preceding primitive band. Probably the latter will always be the case where the young are hatched as true _Nauplii_ (and not merely with a Nauplius-skin, as in _Achtheres_). The two modes of development may occur in very closely allied animals, as is proved by _Achtheres_ among the Copepoda.[9] [1] If the Phyllopoda may be regarded as the nearest allies of the Trilobites, they would furnish, with _Lepidosteus_ and _Polypterus, Lepidosiren_ and _Protopterus,_ a further example of the preservation in fresh waters of forms long since extinguished in the sea. The occurrence of the _Artemiæ_ in supersaline water would at the same time show that they do not escape destruction by means of the fresh water, but in consequence of the less amount of competition in it. [2] “The maxilla of the Decapod-larva (Krebslarve) is a sort of Phyllopodal foot” (Claus). [3] I am still unacquainted with Claus’ latest and larger work, but no doubt the same may be said of it.