JQ2 PORIFERA. I. 



found, which have already been figured by O. Schmidt (Spongien des Meerbus. von Mexico 1880, 

 Taf. IX, Fio-. 10). The earliest stage I have seen, is a quite thin needle, rather shorth- recurved in 

 both ends, and of about the same length as the fully developed diancistron. The development now 

 consists in the needle growing in thickness, the ends increasing in length, and the sharp edges being 

 formed. All phases of this develojiment may be found, as shown in PI. XVIII, fig. i d. It has been 

 a matter of some speculation whether these diancistra were most justly to be termed sigmata or cheke. 

 O. Schmidt (Spong. d. atlant. Gebiet. 1870, 54, and Spong. d. Meerbus. von Mexico, 1880, 82), declares 

 them to be a modification of sigmata, on account partly of their being developed from a phase that 

 he thinks to be sigma-like, partly of their being contort as many sigmata. Carter (Ann. Mag. Nat. 

 Hist. 5, IX, 298), on the other hand, finds by comparing them with the peculiar, contort chela in 

 EspcrcUa {Dcsniacidon] fitiibniis, that they are chelte (• anchorates ), while Vosmaer (The Spong. of 

 cVillem Barents , Bijdr. tot de Dierk., i2te Aflev., 3die Gedelt., 1885, 28) says: ;I call special attention 

 to fig. 85, being a trenchant bihamate with two teeth. This may be a proof that they are modified 

 sanchors and not modified bihamates>. Such abnormities may be found of the diancistra as well as 

 of other silicious bodies, but they surely prove nothing, neither is anything proved by what has been 

 said by Schmidt or Carter, and with regard to the relation between diancistra and the other 

 meniscoid microscleres nothing can be said. The fact mentioned by Schmidt (I.e. 1870, 54, Taf. V., 

 Fig. 17), that the diancistra and especially the sharp edges are not quite silicified, and are more or 

 less destroyed by being boiled, must, as might be thoiight beforehand, be founded upon a mistake; the 

 fact is that they will stand boiling in hydrochloric acid or aqua regia long enough. The form given 

 in fig. 17 c, appears rather to be a quite abnormal form, sucli as may be found. The second kind of 

 diancistra are considerably smaller, but of a similar form, the only differences being that the shaft 

 almost always has a slight curve in the middle, and that the points of the recurved ends come some- 

 what nearer to each other than in the large ones. The edges are here very difficult to see, so that 

 we may easily get the impression that they are wanting. The length is between 0-045 — 0-057'"™, some- 

 times they may be a little longer; the thickness in the middle is 0-004 — 0-007™'". They are developed 

 in the same way as the preceding ones, bus as the edges are only to be seen with difficulty, the 

 developmental phases are far from being conspicuous. Besides the mentioned forms a third form of 

 diancistra is found, which is the smallest of the three; they are highly bent in the middle, and the 

 plane of this curve may be situated differently with regard to the planes through the shaft and the 

 recurved ends. Otherwise the principle of their form is the same as in the two preceding kinds; the 

 edges issuing from the shaft are rather broad, and therefore the notch in the middle of the shaft 

 between the two edges is most frequently distinctly seen ; the edges are also in this form only seen 

 with difficult)-. The length of these diancistra are between 0-021 and 0-028™™, most frequently nearest 

 to the former figure; the thickness in the middle is ca. o-ooio™™. Of these three different forms of 

 diancistra the largest ones occur in a peculiar way, being attached to the fibres of the skeleton with 

 one end, while the other end projects, and they are collected in bundles situated along the fibres with 

 certain intermediate spaces, in the same way, as Topsent (Resultats des Camp, scient. du Prince de 

 Monaco, Fasc. II, 1892, 87, PI. VII, Fig. 4) mentions and figures for the species determined by him as 

 H. fo]insoni\ on the other hand the\- are not found in the dermal membrane or in the membrane lining 



