354 Mr. II. J. Carter on the Hexactinellida?. 



others for specific distinction ; but while the former remain 

 under all circumstances in the dried specimen, tlie latter, unless 

 accidentally included in the material which binrls together the 

 large spicules (a very rare occurrence), Avill, if the sarcode has 

 passed into dissolution before the specimen is taken up for 

 preservation, inevitably fall through the reticulated structure 

 of the skeleton, as small pebbles through the meshes of a 

 fishing-net. Hence the distinguishing character furnished by 

 the minute or flesh-spicules will be lost or retained as the case 

 may be ; while, as some sponges have no minute spicule^ 

 its absence then must be determined by the presence of the 

 sarcode, since if the sarcode be preserved the minute spi- 

 cule will be in it if there be one, and if not the contrary. 

 Thus it should be remembered that a sponge possessing the 

 flesh-spicule in the natural state may not have it in the dried 

 one, and that this remark applies to the Spongiadge generally. 



So far, all the Hexactinellidas that have been made known 

 possess a minute or flesh-spicule in the form of a " rosette," 

 which may be defined to be an equiarmed, sexradiate spicule, 

 from the ends of whose arms respectively proceed a certain 

 number of rays which, although the same on each arm of the 

 specimen, may vary in form, number, and arrangement with 

 the species, but always project from the ends of the arms, which 

 corresponding to the six sides of a cube, the whole, when the 

 spicule is perfect, forms a more or less spherical rosette. 



The term " rosette " first appears in Dr. Bowerbank's 

 * British Spongiadse ' (vol. ii. p. 189 &c.), as indii-ectly applied 

 to a globular group of inequianchorate spicules well delineated 

 in his plate xviii. fig. 297 (vol. i.^ op. cit.) as illustrations of 

 an Esperia {Hymeniacidon lingua, B.). These are also flesh- 

 spicules. Then Prof. Thomson, in describing Askonema 

 (' Depths of the Sea,' p. 428), directly applies the term to the 

 flesh-spicules of this sexradiate sponge. I now intend to 

 apply it generally to the flesh-spicules of the Hexactinellidje 

 which possess this form, designating it according to its 

 diflerences in a way which I hope will be found less oppressive 

 to the memory, and therefore more practicable, than Dr. 

 Bowerbank's " Terminology." 



As before stated, we find in most sponges two distinct classes, 

 of spicules, viz. those which" belong to the skeleton (skeleton- 

 spicules) and those which belong to the sarcode (flesh- 

 spicules). The skeleton-spicules sooner or later are all involved 

 in the formation of this structure, while an enclosure of the 

 latter is an exception so rare that the flesh-spicule maybe said 

 never to become united to the skeleton-structure. However 

 remarkable it may be that the flesh-spicules should be inti- 



