504 DR. J. S. BOWERBANK ON [June 15, 
conformable, both as regards each other and the large primary fibres 
of the skeleton; and I could not detect a single floricomo-sexradiate 
one among them. The simple rectangulated sexradiate spicula, 
when immersed amid the skeleton-fibres, usually had the whole of 
the six radii developed; but those at the inner margin of the great 
incurrent areas were frequently deficient of the distal axial ray, so 
that the four lateral rays were presented in the same plane as that 
of the inner margin of the great incurrent areas. 
On examining the outer surface of the specimen we find a mar- 
vellously beautiful compound reticulated dermal skeleton elevated 
slightly above the general surface of the sponge-structures beneath. 
This exquisitely beautiful tissue is composed of a single layer of 
slender, simple, rectangulated sexradiate spicula, conformably ar- 
ranged in the same plane, the long proximal ends of the central 
shafts being all pointed downwards towards the skeleton beneath, 
while the lateral radii of each spiculum glide over those of their 
next neighbours until the distal ends of their respective rays closely 
approach to the central shafts of each other, thus systematically 
interlocking with each other, and forming a beautiful quadrangular 
network in the dermal stratum. The distal portion of the central 
shaft of each simple rectangulated sexradiate spiculum has a single 
floricomo-sexradiate spiculum cemented to its apex, forming a uni- 
form stratum at regular distances of these beautiful objects imme- 
diately beneath the outer surface of the dermal membrane. 
The interstices of the quadrangular network are filled by a thin 
translucent membrane on which there are occasionally found, closely 
adhering to the membrane, groups of five or six minute quadrifurcate 
sexradiate stellate spicula, very similar in general structure to those of 
Iphiteon Ingalli, figured in the Society’s ‘ Proceedings’ for 1869, 
plate xxiii. fig. 2, p. 331—but with this difference, that the radii of 
those of I. Ingalli are spinulate, while those of 4. speciosum are at- 
tenuated to exceedingly sharp distal terminations. These spicula are 
very slender and delicate in their proportions, and require a power 
of at least 400 linear to render them distinctly to the eye. A fully 
developed one measured as follows:—extreme diameter z}z inch; 
diameter of the sexradiate basal portion =, inch; length of the 
furcating radii +755 inch; and the diameter of the thickest portion 
of fureating radii =3},5 inch. 
Thus these beautifully constructed and elaborately arranged organs 
form most effective defences against minute annelids or other insidious 
enemies who may attempt to prey upon the soft gelatinous tissues of 
the sponge. A single mouthful of the minute sharp-pointed spicula 
of which their beautiful floral terminations are constructed would 
effectually deter these predacious little enemies from any further 
attacks upon the soft tissues of the sponge. A more complete or 
more effective mode of disposition of these wonderful defensive 
organs cannot possibly be conceived. These structures are amazingly 
beautiful to our eyes; but their admirable adaptation to their especial 
purposes infinitely surpasses their beauty in our estimation. To re- 
turn to the peculiar mode of construction of the rectangulated net- 
