Crustacea, than with those of the lower Crustacea, though in mere shape they more nearly resembled the latter. [69] 'Annales des Sciences Naturelles,' 3d series, tom. xvi, pp. 233, 236, 237. _Cementing Apparatus._ (Plate 28.) I have already (p. 128) given an account of the manner in which, in the pupa of Lepas, the cement-tissue escapes from the prehensile antennæ, and of the structure of the cement-ducts, and of the cement-glands or incipient ovaria; and likewise of the changes by which these organs assume their ultimate form in the mature Cirripede. In my former volume, on the Lepadidæ, I described the cement-glands and the cement-tissue in several genera, and I have there shown (singular as the fact is) that the two cement-glands, with their contents, actually consist of ovarian tubes with their contents (for there seemed to be a relation in the state of fulness in both) in a modified condition. In the Balanidæ, I am not able, from the difficulty of the dissection, to confirm these conclusions, excepting in so far that the tubes on which the cement-glands are formed, run into the mass of ovarian cæca; but, I may add, that in the abnormal Proteolepas, belonging to another Order (see the section, Pl. 24, fig. 1), nothing could be plainer than that the membrane of the ovarian sack (_b_) formed the cement-ducts, and that their cellular contents, which within the sack (_a_) were in process of conversion into ova, within the ducts were converted into the cement-tissue. This cement, by some unknown power, travels down the ducts, and debouches at the antennæ.