352 Mr. H. J. Carter on the HexactineTlida?. 



(Annals, vol. ix. p. 430, pi. xxii. fig. 16, June 1872). The 

 ornamental parts, such as spines &c, although no doubt 

 in the original design, are not attended by any alteration in 

 the central canal, and therefore do not belong to the " spicule 

 proper." I call the " spicule proper" that fundamental form 

 which is marked out by the central canal and its branches ; and 

 these do not run into the ornamental portions. 



But whatever may be the terms finally adopted for the 

 spicular systems of the Hexactinellidfe and Lithistidae respec- 

 tively, it is perfectly evident that in the grouping of these 

 sponges we cannot include the sarcospiculous Hexactinellidaj, 

 viz. Hyalonema &c, under either of the terms " Corallio- 

 spongia" or " Vitrea ;" while the name " Hexactinellidse " 

 refers rather to the elements than to the general character of 

 these sponges. 



All sponges begin their development from the ovum in the 

 form of a sarcodic embryo ; after which come the spicules, 

 and lastly the fibre, which converts the skeleton-spicules into 

 an axis, whether this fibre be vitreous or horny. Hence, as 

 the sarcodic precedes the vitreous state, the latter would rank 

 as a superior development to that of the sarcospiculous Hex- 

 actinellidse, in which the sarcode never passes into either horny 

 or vitreous fibre, but remains simply hardened and amorphous. 

 So it seems to me desirable that we should discard this 

 " order " altogether, and distribute the groups of the Hexacti- 

 nellidse among the divisions of the Spongiadse in accordance 

 with what I have proposed in the footnote to my paper on 

 the points of distinction between the Spongiadse and Foramini- 

 fera (Annals, vol. xi. pp. 355-356, May 1873). 



To understand this suggestion, however, it is necessary to 

 premise that the vitreous fibre of the Hexactinellidse is merely 

 homy fibre silicified, and that the spicules of the species are 

 imbedded in this, after the same manner respectively as they 

 are imbedded in the fibre of sponges generally. This being 

 the fact, we might expect to find certain Hexactinellidse with 

 their spicules all confined to the interior of the silicified fibre, 

 as the spicules in the horny fibre of my third division, viz. the 

 " Chalinidse " — then that the fibre in another group of the 

 Hexactinellidse is more or less echinated with spicules in 

 addition to those contained in the interior, as in my fourth 

 division, viz. the " Armatse " — or the spicules supported by 

 amorphous sarcode alone, as in the fifth division, viz. the 

 11 Renierinse," wherein, too, would come our quadriradiate 

 system, or Schmidt's " Lithistidae," in which I think the 

 filigreed terminations of the arms interlocking with each other, 

 rather than the presence of vitreous fibre, chiefly bind the 



