Sponges from South Australia. 203 



spectively in the vents mentioned. Triradiate, keratose 

 spicule, whose angles are equal and arms about 85-1 SOOths 

 in. long by 4-1 SOOths 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. 

 Hob. 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 " Aplysina corneostellata^ ('Annals,' 1872, vol. x. 

 p. 105, pi. 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 'Annals' of 1881 (vol. viii. p. 118) to the 

 observations of Fritz Miiller, who first described and illus- 

 trated Darwinella from a specimen found on the shore of 

 Desterro, in Brazil (Archivf. mikroskop. Anat. 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 examination'of 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 central 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 Johnstonii. 



