16 Mr. H. J. Carter on the Polype-like 



Cliona every here and there makes holes through this crust 

 or thalloid froud for its pore-arege or vents as required. 



Of course, therefore, these "holes" are occupied by a longer 

 or shorter cylindrical prolongation of the sponge (fig. 36, h) in 

 proportion to the thickness of the crust, which thus presents 

 as many heads ; so that when the shell is dissolved off by 

 acid, these heads project here and there above the general 

 surface of the sponge (PL II. fig. 33, a, h). 



It may be assumed that this way of reaching the exterior 

 necessitates a cylindrical extension of this kind ; but Grayella 

 cyathophora^ which is an allied species, possesses it, together 

 with a branched system of excretory canals, although freely 

 spreading over the surface of the rocky object on which it may 

 be growing. 



Each portion, too, in Cliona corallinoides has, for the 

 most part, its peculiar spicule. Thus the pin-like, slightly 

 curved, and fusiform one with oval head (fig. 37, a) is almost 

 entirely confined to the cylindrical head-like extensions of 

 the sponge, and the tentacle-like prolongations of the pore- 

 area, where their points project outwardly (fig. 35, f), while 

 the minute sinuous spinous spicule (c, d) for the most part 

 fills up the interstices between the latter, and the curved, 

 acerate, spinous spicule {b), which is not more than a quarter 

 the length of the pin-like one, is confined to the areolar struc- 

 ture of the interior. These spicules, as they are described, 

 average about 83, 2-3|, and 21 6000ths of an inch in length 

 respectively. 



When we examine the heads or free ends of the cylindrical 

 prolongations, -they are found to be of different sizes, to pre- 

 sent an irregularly round or elliptical margin (fig. 34, a a a), 

 and within this a variable number of tentacle-like prolongn- 

 tions of the sponge-structure {b b b) charged with the pin-like 

 spicule, and webbed together by the dermal sarcode (c), in 

 which there is a variable number of pores {d), chiefly situated 

 between the prolongations. In the dried state all this is on 

 a level with the margin of the pore-area, if not a little de- 

 pressed, with the pointed ends of the pin-like spicules un- 

 covered and bristling in all directions (fig. S5,f) ; but in the 

 living state it rises much above the margin, into a convexity, 

 when the dermal sarcode entirely covers and conceals the 

 spicules. 



At this time, inhalant currents may be seen to pass in 

 through the pore-openings. 



Our illustration presents about thirty of these tentacle-like 

 prolongations, of different lengths (PI. II. fig. 34, b b b), and is 

 nearly a facsimile of the mounted dried one from which it has 



