232 DR. J. MURIE ON STEERE'S SPONGE, 



sciously brought, and subsequently figured among the root-detritus of Prof. Owen's Euplectella cucumer, 

 still where it was then, viz. in the possession of Dr. Arthur' Farre (Trans. Linn. Soc. vol. xxii. pi. xxi. 

 fig. 1), with a microscopic portion, highly magnified in fig. 8, which had been "discovered by Dr. Farre" 

 himself, and thus had been thought worth figuring independently of the Euplectella — showing, as the 

 sequel will prove, that the peculiarities of the structure had not passed unnoticed, although the sponge 

 itself had not been discovered. 



Lastly, it is worthy of remark that Dendrospongia appears to exist in the neighbourhood of the Euplec- 

 tellas both at the Seychelles and among the Philippine Islands. 



Besides the fragments of Dendrospongia Dr. Farre also discovered another structure, which Prof. Owen 

 likened to a "harrow" (I. c. figs. 9, 9a). After this Dr. Bowerbank obtained permission of Dr. Farre to 

 examine the entire specimen of Euplectella cucumer, and (among other fragments) brought away with him 

 specimens respectively of those discovered by Dr. Farre, to which I have above alluded. These Dr. 

 Bowerbank examined, described, and figured respectively, under the general name of Farrea occa (Proc. 

 Zool. Soc. 1869, pi. xxiv. figs. 1 and 7), conceiving the " harrow-like tissue " to have belonged to "the 

 dermis," and the other structure to the body of this sponge. 



"We know, however, now, from entire specimens of the sponges represented by these two structures, 

 that they belong to two distinct species, and that the " harrow-like tissue " is the 6ooft/-structure of 

 Farrea occa, and not identical with the dermal layer of the Hexactinellida, probably existing (according 

 to Dr. J. Millar, who first directed especial attention to it) throughout all the species, although often, 

 from its delicate structure, more or less rubbed off. 



In 1873, just after having, by the kind assistance of Dr. Farre, examined his justly celebrated specimen 

 of Euplectella cucumer myself, I also brought away specimens of the structures figured both by Professor 

 Owen and Dr. Bowerbank (I. c), and, having examined them microscopically, came to the concluf ion that 

 the " harrow-like tissue '■' should remain as Farrea occa, and the other structure be designated Farrea 

 densa, as belonging undoubtedly to a different sponge (Ann. & Mag. Nat. Hist. 1873, vol. xii. p. 454, 

 pi. xvii. fig. 5) . Hence a fragment of the latter with its peculiar spines was figured (I. c. fig. 6), mention- 

 ing also (p. 463) that among the spicules boiled off from this fibre was a scopuline one like that of 

 Aphrocallistes beatrix (which is nearly identical with that of Dendrospongia) " in great abundance." 



As soon, therefore, as Dr. Murie, through Dr. J. Millar, kindly put me in possession of an actual fragment 

 of Dendrospongia, I saw that the body-fibre was identical with that of Farrea densa, and that the scopuline 

 spicules were also identical, but I had observed no rosette. However, on turning to a mounted specimen 

 which had not been boiled in nitric acid, I found not only the rosette but the peculiar head of one of the 

 scopuline spicules also present with the body-fibre. It may be here remarked, respecting the rosette, that 

 Dr. Marshall states (Zeitschrift, /. c. p. 185) " bei Sclerothamnus und Aphrocallistes findet sich keine 

 analoge Nadelform." Thus we have traced Dendrospongia back to the Linnean Transactions of 1857. 



Whether Farrea densa, Sclerothamnus Clausvi, or Dendrospongia Steerii is to take precedence in nomen- 

 clature I care not. Dr. Murie's description and illustrations take precedence with me as to accuracy and 

 fullness of detail. This lasts for ever ; but a name may be disputed to the end of time. 



Dendrospongia Steerii evidently belongs to that group of sponges which possesses for one of its pecu- 

 liarities the scopuline spicule, which must not be confounded with the rosette that, so far as my obser- 

 vation extends, always accompanies it. The scopuline spicule is often taken into the skeleton-fibre, and 

 therefore may be regarded as a subskeleton spicule ; while the rosette, being essentially a flesh-spicule 

 (that is, confined to the sarcode) is seldom or never included in the vitreous fibre. Hence, if the skeleton- 

 fibre alone remains, the rosette (as was probably the case in Dr. Marshall's specimen) may have fallen 

 through it on the decomposition of the sarcode, since, as I have before stated, when this takes place the 

 rosette passes out through the skeleton almost as easily as small pebbles through the meshes of a fishing- 

 net. In such instances, therefore, the absence of the rosette may not indicate that there never was any. 

 The rosette, again, often presents itself under a variety of forms in each species of the Hexactinellida, 

 as described and figured by Dr. Murie in Dendrospongia Steerii. 



