280 THE VOYAGE OF H.M.S. CHALLENGER. 



to tlie proximity of the axial cross of the next spicule, where they are rounded off and 

 terminate, they are sometimes continued right along to the middle of the second spicule ; 

 thus three axial canals may not unfrequently be seen running alongside in one strand. 



In his last description of Farrea occa ^ Carter states that the conical prominences 

 which project freely on either side of the narrow meshed lattice-work are bent outwards. 

 I cannot, however, admit the accuracy of this as a general statement. As a rule the 

 prominences are straight and directed at right angles to the surface. As Carter correctly 

 notes, they gradually decrease in length towards the base of the stock. 



As to the loose parenchymalia lying between the beams of the dictyonal framework, 

 I shall first discuss the uncinata. These have been already well described and figured 

 by Carter (/oc. cit.). His description is as follows :— " Acerate, straight, unsymmetrically 

 fusiform, that is, the outer or j)rojecting part being thicker than the inner two-thirds 

 of the spicule, which is thus rendered long and whip-like ; sharp-pointed at each end, 

 spined at short intervals throughout, the spines long, smooth and slender, respectively 

 supported on bracket-like processes, which, being spirally arranged around the shaft, give 

 it an iri-egular zig-zag appearance, all sloping in the same direction, that is backwards, or 

 towards the sponge, at a very slight angle upon the shaft, whose outer or thickened end is 

 extremely sharp." He calls them barbulas,^ a diminutive of the English barb, and says 

 that they are " common to almost all the Hexactinellida." This assertion I cannot, how- 

 ever, admit. Among the numerous Lyssacina which I have examined, structures like 

 these uncinates only occur in the genera Pheronema, Polio])ogon, and Semjyerella. 

 Among the Dictyonina I have not found them in the genera Myliusia, Gray ; Dacty- 

 localyx, Gray, Scleroplcgma, 0. Schmidt, Ilargaritella, 0. Schmidt, Euryplegma, 

 F. E. S., Joanella, 0. Schmidt, and Aulocystis, F. E. S., and these may therefore be 

 designated as Inermia, in opposition to the Dictyonalia with uncinates — the Uncinataria. 



As Carter notes, the uncinates exhibit in Farrea occa an extraordinary variability 

 in length, though this depends to some extent on the age of the individual uncinates and 

 of the regions of the sponge in which they occur. Further, in the form, number, and 

 arrangement of their inturned spines, there are in one and the same sponge very marked 

 difierences. Earely, and only in the younger portions of the tubes, I find the spines 

 distant and very divergent from the stem as represented in PI. LXXI. fig. 4, and 

 PI. LXXIH. fig. 3. Sometimes a spiral arrangement of the spines can be detected; in 

 other cases this is impossible, and the distribution appears to be quite irregular. The 

 expansion of the distal third portion of the uncinates as contrasted with the interior is 

 very marked, especially on the large and strongly developed forms, where, too, the inner 

 end is not unfrequently distinguished from the outer by the development of weak spines. 



' Arm. and Mag. Nat. Hist, ser. 5, vol. sv. p. 388. 



^ Since I had used the Latin term uncinatum (a rod beset with barbs) before I received Carter's memoir, and since 

 Latin or Greek terms seem to me to have the preference as being cosmopolitan and not national, I have adhered to my- 

 original designation. 



