130 Mr. H. J. Carter on Specimens 



simple or subdivided, are for the most part spread out among 

 and support a layer of siliceous balls or globules on the sur- 

 face, called the " cortex " or petrous crust; while the shaft is 

 directed perpendicularly inwards ; and thus, in juxtaposition, 

 it forms in combination around the Geodia a more or less 

 distinct zone, whence its name. 



2. " Body-spicule." This, which is acerate, fusiform, 

 smooth, and curved, is generally the next in size to the zone- 

 spicule, but by far the most numerous, as it is not only the 

 staple spicule of the body, but, when associated with the 

 zone-spicules, lies parallel with them, projects into the cortex, 

 and thus adds to the strength of the zone generally, as well 

 as the cortex. 



3. " Forks " and " anchors." These are essentially anchor- 

 ing-spicules, and, from the embryo upwards, are, as a matter of 

 course, projected beyond the surface. They are trifid; but 

 whereas in the "fork " the arms or prongs are produced, they 

 are recurved in the " anchor," while the shaft in both, which is 

 very long, depends for its length upon the distance the heads 

 are beyond the Geodia. From their great delicacy and brit- 

 tleness, they are for the most part broken off, especially 

 the anchor-heads ; their presence among the zone-spicules 

 preparatory to their exsertion is thus frequently the only 

 evidence, of their existence ; and here they appear to be for 

 any purpose but that of " anchoring " or fixing the Geodia. 

 Hence their office is often overlooked. 



4. " Siliceous globule." This is developed in the interior, 

 where it may be seen in all stages of growth till fully formed, 

 when it appears to be transferred to the surface, where, in 

 combination, it forms the cortex or petrous crust, in which 

 there are no young forms. In its earliest stage of develop- 

 ment, or when it is but just visible, it appears to be stelli- 

 form ; the rays then become multiplied, extended, and hair- 

 like; after which, as they grow outwards, they become united 

 into a crystalline mass, which finally assumes a more or less 

 compressed, spheroidal, or elliptical form; meanwhile a hilous 

 depression becomes apparent on one side ; and finally the 

 rest of the surface is covered by little stelliform bodies in 

 juxtaposition, which are respectively supported by the rays, 

 now undistinguishably consolidated into a crystalline mass. 



5. " Stellates." There are always two forms of stellates,both 

 of which are very minute — but one much smaller than the 

 other ; and this is chiefly confined to the surface, where it 

 densely charges and thus strengthens the pore-bearing dermal 

 sarcocle.- The other or larger form is chiefly confined to the 

 sarcode of the interior (for they are both flesh-spicules), where 



