[2] nIn the genera _Orchestoidea, Orchestia, Allorchestes, Montagua, Batea_ n.g., _Amphilochus, Atylus, Microdeutopus, Leucothoë, Melita, Gammarus_ (according to Meissner and La Valette), _Amphithoë, Cerapus, Cyrtophium, Corophium, Dulichia, Protella_ and _Caprella._ote [3] Little as a name may actually affect the facts, we ought certainly to confine the name “micropyle” to canals of the egg-membrane, which serve for the entrance of the semen. But the outer egg-membrane passes over the “micropylar apparatus” of the Amphipoda without any perforation, according to Meissner’s and La Valette’s own statements; it appears never to be present before fecundation, attains its greatest development at a subsequent period of the ovular life, and the delicate canals which penetrate it do not even seem to be always present, indeed it seems to belong to the embryo rather than to the egg-membrane. I have never been able to convince myself that the so-called “inner egg-membrane” is really of this nature, and not perhaps the earliest larva skin, not formed until after impregnation, as might be supposed with reference to _Ligia, Cassidina_ and _Philoscia._ [4] According to Spence Bate, in _Brachyscelus crusculum_ the fifth abdominal segment is not amalgamated with the sixth (the tail) but with the fourth, which I should be inclined to doubt, considering the close agreement which this species otherwise shows with the two species that I have investigated. [5] In the young of _Hyperia galba_ Spence Bate did not find any of the abdominal feet, or the last two pairs of thoracic feet, but this very remarkable statement required confirmation the more because he examined these minute animals only in the dried state. Subsequently I had the wished-for opportunity of tracing the development of a _Hyperia_ which is not uncommon upon Ctenophora, especially _Beroë gilva,_ Eschsch. The youngest larva from the brood-pouch of the mother already possess _the whole_ of the thoracic feet; on the other hand, like Spence Bate, I cannot find those of the abdomen. At first simple enough, all these feet soon become converted, like the anterior feet, into richly denticulated prehensile feet, and indeed of three different forms, the anterior feet (Fig. 44) the two following pairs (Fig. 45) and finally the three last pairs (Fig. 46) being similarly constructed and different from the rest. In this form the feet remain for a very long time, whilst the abdominal appendages grow into powerful natatory organs, and the eyes, which at first seemed to me to be wanting, into large hemispheres. In the transition to the form of the adult animal the last three pairs of feet (Fig. 49) especially undergo a considerable change. The difference between the two sexes is considerable; the females are distinguished by a very broad thorax, and the males (_Lestrigonus_) by very long antennæ, of which the