1867.] DR. BOWERBANK ON ALCYONCELLUM SPECIOSUM. 355 



are immersed in the sand, as appears to have been the case with the 

 greater number of the specimens that I have examined, or when in- 

 serted in, or adherent to the tissues of another sponge, as in the case 

 of the specimen in the possession of Dr. A. Farre. The recurvo- 

 quaternate terminations of their distal ends ai'e short and stout ; and 

 the terminal boss whence they spring is very strongly produced, so 

 as to give them great retentive power. There are usually but four 

 hooks ; but in one instance I observed that number was doubled by 

 each ray being replaced by two somewhat smaller ones. The shaft 

 of the spiculum is barbed alternately at nearly regular distances for 

 about one-fourth of its length from the recur vo-quaternate apex, the 

 barbs pointing towards the smooth attenuating basal portion of the 

 shaft, and they decrease in length and number from the apex of the 

 spiculum downward. The structure of the apex of the fibre, com- 

 bined with the numerous stout spines of the distal portion of the 

 shaft, gives them remarkably strong prehensile power. These organs 

 occur in large fasciculi, each consisting of numerous spicula. Tlieir 

 basal portions are clustered around the primary lines of the skeleton 

 near their bases, and are firmly cemented to them for about a half 

 or one-third of their length, from which attachment they ulti- 

 mately pass oflF, diverging in various directions in search of points of 

 adhesion. Their length frequently exceeds 3 inches. Athough sili- 

 ceous, they are remarkably flexible and strong. The shaft consists 

 of numerous concentric layers containing comparatively a large 

 amount of animal matter. 



The structure of the fibre of this sponge is solid and siliceous, like 

 that of Bactylocalyx ; but the mode of its disposition in the skeleton 

 is very different. The primary lines consist of nearly parallel con- 

 tinuous fibres anastomosing laterally at irregular distances ; so that 

 in the aggregate they form a single circular series of strong and rigid 

 compound columns of support bounding the large tubular internal 

 cavity, and firmly braced in their proper positions by the secondary 

 series of similarly constructed fibres, placed at right angles to the 

 primary ones. This arrangement is further strengthened by nume- 

 rous small fibres disposed in various diagonal lines to the primary 

 and secondary series of the skeleton-tissues. This admirable ar- 

 rangement produces a structure combining the greatest amount of 

 lightness, strength, and beauty that can well be conceived to exist 

 in nature. At a short distance above the ba^e of the sponge it is 

 farther strengthened by numerous strongly produced angular ridges 

 of fibrous tissue disposed in lines which are always more or less dia- 

 gonal to the long axis of the sponge, and usually somewhat flexuous. 

 The ridges are but slightly produced near the base of the sponge, 

 but they increase both in height and strength as they approach its 

 apex. Tlie summits of the ridges are composed of strong lines of 

 anastomosing fibres ; and two or three such lines of fibres are fre- 

 quently to be seen beneath the outer one. These ridges do not ap- 

 pear to have ever formed portions of the terminal ridge or frill of 

 the sponge, bounding the oscular area, although they agree perfectly 

 in the mode of their structure ; and it is probable that the circular 



