]18 A MONOGRAPH OF THE 



to which he refers as being of an orange colour when fresh, 

 and that it also was a dwarf specimen of his S. stupom; 

 if so, S. rigida of Montagu and Halichondria rigida of 

 Johnston's 'British Sponges' are no longer species, but syno- 

 nyms only. 



The specimen of B. stupoms which I received from Mr, 

 M'Andrew is in better condition than any one of the 

 species that I have yet seen. The thickness of the sarcodous 

 substance surrounding the skeleton is equal to about one 

 third of the diameter of the latter, and in this fleshy coat 

 comparatively very few spicula are disposed in a longitu- 

 dinal direction. Very large attenuato-acuate spicula, as 

 compared with the largest of the spicula of the skeleton, 

 are projected from the cylindrical axis through the sur- 

 rounding fleshy mass at irregular distances. In this spe- 

 cimen the sp hero-stellate spicula are in their normal 

 position, immediately beneath the dermal membrane ; they 

 are exceedingly numerous, and are seldom more than twice 

 their own diameter apart from each other, but there appears 

 to be but a single layer of them, and it very rarely occurred 

 that a specimen was foimd deeply imbedded in the fleshy 

 mass, and 1 could not find any in the sarcode within the 

 axis of the skeleton. 



The tension spicula are very abundant. They are princi- 

 pally disposed around the axis in numerousirregular,flatfasci- 

 culi, lying usually in the direction of the axis of the sponge, 

 a few of them only occurring at right angles to it ; others 

 are dispersed singly and irregularly amid the membranous 

 tissues, and immediately beneath the dermal membrane. 



The presence of the sphero-stellate spicula in the fleshy 

 substance of H. stuposa, Mont., distinguishes this species 

 readily from all its congeners, and it should be remembered 

 that these spicula are not usually perceptible under ordinary 

 circumstances, but must be rendered so by boiling in nitric 

 acid and mounting in Canada balsam. Montagu's figure, 

 although roughly executed, is extremely characteristic, and 

 the projection of the surface spicula in the dried specimen 

 to a greater extent than the whole diameter of the axis of 

 the sponge is by no means exaggerated. The axis, when 



