Sponges from South AusfraUa. 437 



of subdivision of these canals, that is, of course, where the 

 latter are very small the holes are in proportion. 



It may also be observed that the chambers immediately 

 under the pore-dermis are often much more dilated than 

 further in, thus resembling the " subdermal cavities " of the 

 non-calcareous sponges ; and a similar dilatation may often 

 be seen immediately under the cloaca, which, to a certain 

 extent, may account for the plurality of openings in the wall- 

 structure appearing- through the holes of the latter, as will be 

 noticed hereafter in the descriptions of the respective species 

 where this presents itself; I say " to a certain extent,^' be- 

 cause where the holes in the cloaca are in proportion to the 

 number of radial chambers, as in Grantia ciliata &c., this 

 cannot occur. 



Lastly we come to the " spiculation," i. e. a description of 

 the different forms of spicules, which are generally found to 

 be more or less constant in particular parts. Thus, beginning 

 with the acerates, it will be noticed that those which fringe 

 the vent or mouth of the cloaca present a peculiarly glistening 

 aspect en masse, which, when they are separate, is found to 

 depend on their long, straight, cylindrical, delicate form, 

 closely resembling " spun glass," and these, similarly pointed 

 at each end and arranged like a palisading around the inside 

 of the mouth, where their fixed ends are on a level with the 

 surface of the cloaca and their free ones project more or less 

 beyond the mouth or vent, will be called the "peristome;" 

 on the other hand, when there are none, and this feature is 

 consequently absent, the mouth will be called "naked." At 

 the same time it should be remembered tliat the two s1;ates 

 may occur in a group of the same individuals, so that the 

 presence or absence of the " peristome " must not be always 

 regarded as an infallible distinction. 



Again, the acerates may be more or less scattered over the 

 surface either echinatingly or altogether imbedded in it lonji- 

 tudinally, when they will generally be found to be much 

 stouter, more or less curved equally throughout, or more in 

 one half than the other, which is generally the outside one ; 

 also more or less equally fusiform, in which case the thickest 

 part is outAvards and the other more or less sunk into the wall. 

 Occasionally the outer end is " lanciform," in a line with the 

 shaft, or bent to one side, like a " fixed bayonet " on a mus- 

 ket, and limited in its extent by a more or less prominent 

 annular inflation, which extends obliquely or circularly across 

 the shaft at the point of union ; or the outer end may be 

 more or less sharply curved or club-shaped &c. 



Lastly, there is often a minute straight or sinuous acerate 

 Ann.& Mag. N. Hist. Ser. 5. Vol. xvii. 30 



