456 Mr. H. J. Carter on the LVI. — Further Instances of the Sponge-Spicule in its Mother Cell Bj H. J. Carter, F.R.S. &c. [Plate XXI. figs. 26 & 27.] Since my description and figures of the mother cell of the sponge-spicule were published (' Annals,' 1874, vol. xiv. p. 100, pL X.), I have met with two more examples where the cells respectively enclosed a single tricurvate (flesh-spicule) so nearly approaching in length and form (in one instance especially) to a skeleton-spicule, tliat I have given representa-tions of them in Plate XXI. figs. 26 & 27, to show also how a long, linear spicule may be thus enclosed throughout in an equally long, bolster-shaped or tubular, nucleated sponge-cell. Figure 26 comes from a variety of Esperia cegcKjrojyilciy Carter ; and although much thinner than the skeleton-spicule of this species, it is so sliglitly undulous and so much longer than the latter, that it might be easily mistaken for a second form of skeleton-spicule, which is contrary to one of the characters that I have assigned to the Esperiadre, viz. that they only possess one form of skeleton-spicule. Finding it, however, in a cell (fig. 26, Z>), and seeing it more tiicurvate in form in the ovum of the parent (fig. 25), there was no difficulty in con-cluding that it was the tricurvate of this variety of Esperia oigagropila. As it appears in the adult it is linear, veiy thin, smooth, slightly undulous (fig. 26, a), and longer than the skeleton-spicule both in the parent and in the ovum which has nearly arrived at the embryonal degree of development (fig. 25, e) ; so that we may fairly assume that this, wdiich is the chief peculiarity of the variety, is constant. In measurement it is more than twice the length of the tricurvate in the typi-cal species, which, on the other hand, gains in stoutness what it loses in length, the former being 90-6000ths inch long. Growing in small patches scantily on the rocks (at Budleigh-Salterton) towards low-water mark, it (with the exception of possessing a much smaller bihamate) agrees Avith the typical species, viz. Es^peria cpgagropila, in the form and size of its single inequianchorates as well as in their rosette-forms, together with all the other characteristics of the latter. Figure 27, on the other hand, comes from a distinct species of MiCROCiONA, Bk., in which the small, abruptly subangular form of the tricurvate in the centre of the spicule contrasts strongly with its greatly extended and almost straight arms. Ending in spined extremities, however, causes it to differ from all the species described by Dr. Bowerbank, although that called "J/. armata'''' (B. S. vol. ii. p. 129) seems to come so near to it that I cannot help thinking that, if it had been more accu-
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