Darwinella australiensis, Gunther & Dallas & Carruthers & Francis, 1885

Darwinella australiensis View in CoL , n. sp.

Massive, sessile, lobate; lobes simply convex, or com ­ pressed and elongated horizontally into meandriniform, thick, erect, and branching ridges. Consistence soft, resilient. Colour, whim fresh, “ Venetian red,” now dark grev flesh ­ colour. Surface conulated, conuli about l-8th in. apart, terminated respectively by a single filament or fibre, which gives a hairy appearance to the whole, supporte 1 in the in ­ terval by a beautifully soft ami fleshy fibro-reticulate l dermis charged abundantly with triraliate keratose spicules, whose rays intercross and lie parallel to each other respectively, so as to leave interstices in which the pores are situated. Vents numerous on the prominent parts of the convex lobes and along the ridges of the compressed ones. Fibrous structure loose, widely reticulated; main or vertical branches composed of a thin cylindrical wall of dark amber-coloured keratine, cored, as usual,-with a light grey granulo-flocculent substance, but with the “ core ” much greater in diameter than the thickness of the keratose wall, so that the fibre collapses on desiccation, which is the opposite to that which obtains in the Luflarida; hence this is the chief distinction. Lateral or small fibre very scanty, its place being supplied by the tri ­ radiate keratose spicules with which the parenchyma is as much supplied as the dermis; the whole traversed by the branches of the excretory canal-systems which terminate re ­ spectively in the vents mentioned. Triradiate, keratose spicule, whose angles are equal and arms about 85-1 SOOths in. long by 4-1800ths in. wide at the base, cored through ­ out by a canal which is formed of conical layers of keratine given off successively from a granuliferous cell in the centre, diminishing in size with the diameter of the ray, generally presenting the commencement of a fourth ray in the centre in the form of a minute tubercle, which is a bud of the central cell, and, although most frequently of microscopic size, is sometimes fully developed, thus causing the spicule to become quadriradiate; while, on the other hand, sometimes only two rays are developed from the central cell, viz. in opposite directions, which gives it the so-called “ monactinellid ” or acerate form. Size of the largest specimen, of 'which there are several and all comparatively small, about 2 in. high by 2x2 in. horizontally.

Hab. Marine.

Loc. Port Phillip Heads, South Australia. Depth 19 fath.

Obs. This undoubtedly is a Darwinella , like the species from the N.W. coast of Spain, which, ignorant at the time of Fritz Muller ’s discovery, I described and illustrated under the name of 11 Aplysina corneostellata ” (‘Annals,’ 1872, vol. x. p. 105, pl. vii.). The Australian species chiefly differs from the others in the prevailing number of the rays being three instead of four or more.

I must observe here, however, that, although I have alluded in the 1 Annals ’ of 1881 (vol. viii. p. 118) to the observations of Fritz Miillcr, who first described and illus ­ trated Darwinella from a specimen found on the shore of Desterro, in Brazil (Archivf. mikroskop. Amit. Bd. i. S. 344), chiefly for the purpose of opposing his and Oscar Schmidt ’s theory, that the evolutionary development of the mineralized spicule was preceded by the simple keratose form, yet I must admit that, in the examinationof the Australian species, the keratose stellates or triradiates, in their great abundance and arrangement, especially on the surface, together with their origin respectively in a single centred cell (the “ horn-cell,” as I have heretofore termed it), so closely resemble the tri- and quadriradiates of a Calcisponge in these particulars that, how ­ ever much we may be inclined to question the validity of Fritz Muller ’s theory, these spicules, while they appear to supply the place of the “ lateral fibre ” in Darwinella , not only assume the office of the tri- and quadriradiates in the Calcisponges, but in size too are about the same as the large tri- and quadriradiates of our British Leuconia Johnstunii.