[9] Mr. J. D. Dana, who has examined these organs in the larvæ of Lepas, informs me in a letter, that in his opinion they “correspond with the inferior antennæ, the superior being wanting, as in most Daphnidæ.” He continues--“I know of no case in which the inferior are obsolete when the superior are developed; but the reverse is often true.” In position these antennæ certainly correspond to the inferior and central pair of the larva in the first stage, which belong, as it would appear, to the first segment of the body; but judging from the drawing by Burmeister of the larva in the second stage, I am, in some respects, more inclined to consider that they correspond to the larger pair seen within the lateral horns of the carapace in the first stage. [10] Rev. B. L. King. Annual Report of B. Institution of Cornwall, 1848, p. 55. _Eyes._--Close behind the basal articulations of the antennæ, the sternal surface consists of two approximate, elongated, narrow, flat pieces, or segments. These Burmeister considers as the basal segments of the antennæ: as they are not cylindrical, I do not see the grounds for this conclusion: their posterior ends are rounded, and the membrane forming them is reflected inwards, in the form of two, forked, horny apodemes, together resembling two letters, =UU=, close together; these project up, inside the animal, for at least one third of its thickness from the sternal to the dorsal surface. The two great, almost spherical eyes in _L. australis_, each 1/150th of an inch in diameter, are attached to the outer arms, thus, =°UU°=, in the position of the two full stops. Hence the eyes are included within the carapace. Each eye consists of eight or ten lenses, varying in diameter in the same individual from 1/2000 to 3/2000th of an inch, enclosed in a common membranous bag or cornea, and thus attached to the outer apodemes. The lenses are surrounded half way up by a layer of dark pigment-cells. The nerve does not enter the bluntly-pointed basal end of the common eye, but on one side of the apodeme. The structure here described is exactly that found, according to Milne Edwards, in certain crustacea. In specimens _just attached_, in which no absorption has taken place, two long muscles with transverse striæ may be found attached to the knobbed tips of the two middle arms of the two =°UU°=, and running up to the antero-dorsal surface of the carapace, where they are attached; other muscles (without transverse striæ) are attached round the bases, on both sides of both forks. The action of these muscles would inevitably move the eyes, but I suspect that their function may be to draw up the narrow, deeply folded, sternal surface, and thus cause the retraction of the great prehensile antennæ within the carapace.