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substance which at once offers an adhesive surface to which the next 

 grain that may happen to come in contact with it becomes attached ; 

 this is gradually enveloped by the cartilaginous substance, and the 

 same process is repeated until, grain by grain, the whole of the fibre 

 is constructed. Sometimes it happens that after the envelopment 

 of the last, no other grain comes in contact with the termination of 

 the fibre for some time, in this case the cartilaginous substance is 

 projected in the form of a dense yellow thread, the point of which 

 attaches itself, like a sucker, to the surface of the first grain of sand 

 with which it comes in contact, and in this manner numerous single 

 grains may be seen, each supported, as it were, upon a pedestal. In 

 some of these cases the point of attachment scarcely exceeds in dia- 

 meter that of the pedestal, while in others the grain has a third, a half 

 or two thirds of its surface enveloped by the spreading tissue. In 

 some of the most slender fibres there is but a single row of grains, 

 while in others of large diameter they are aggregated so closely and 

 in such numbers as to comprise four or five in a single line of diame- 

 ter. At the spaces intervening between the grains the animal matter 

 is sufficiently dense to render it at all times exceedingly obvious, but 

 it is frequently so thinly spread over the surface of the sand as to ren- 

 der it difficult to distinguish between it and the siliceous matter be- 

 neath, without rendering it opaque by charring it between glasses over 

 the flame of a lamp ; but in this state, and immersed in Canada bal- 

 sam, the thinnest pellicle covering the grains becomes visible when 

 viewed with a power of about 200 linear. 



The grains of sand are usually arranged in the fibre of the sponge 

 in as close and regular a manner as they are in the case of Sabella 

 Belgica, but with this difference ; in the latter the cementing medium 

 is a beautiful cellular tissue, which spreads only so far over the outer 

 surface of each grain as to securely fix it in its place, and in this state 

 appears like a thin regularly reticulated membrane ; while in the 

 sponge the cementing medium is the cartilaginous substance of the 

 sponge, and which, however thin it may be, covers the entire surface 

 of the grains of sand. 



Spicula are of rare occurrence in this sponge. Occasionally two or 

 three are seen grouped together, but usually solitary spicula occur at 

 a considerable distance from each other, imbedded in the exterior 

 coating of cartilaginous matter. They are comparatively short and 

 thick in proportion to their length, and decrease very slightly from the 

 middle to near the points, which are terminated acutely but somewhat 

 abruptly. 



