REPORT ON THE HEXACTINELLIDA. 



The most impo 

 whose greatly proL 

 another in a naannc 

 described. The un] 

 There is not, hower 

 lattice- work. An ii 

 tudinal and transvci 



Delicate and mi 

 closely apposed to i 

 fibres contain numc, 

 ing on their infer i' 

 (PL XIV. fig. 5). 

 marked externally 1 

 numerous spicules ^ 

 scattered rosettes o< 

 work. Among the 

 long bundles of v( 

 occasionally seen pei 



t parts of the quadrate framework consists of strong pentacts, 

 ■d tangential rays are placed in apposition to, and across one 

 milar to that occurring in the species of Euplectellidse already 

 ed ray extends in a radial direction to near the external skin, 

 a special pentact at each of the intersections of the beams of the 

 section without a pentact in fact usually alternates, in the longi- 

 direction, with one which is so provided (PL XIV. fig. 2). 

 extended comitalia, consisting of diacts, triacts, and tetracts, are 

 strong pentact rays. Besides these the longitudinal strands of 

 ; long diacts equipped with upwardly directed barbs, and exhibit- 

 xtremities a knob-like thickened anchor-head with three teeth 

 intersection of the axial canal lies above the latter, and is usually 

 bur barbs arranged in a cruciform manner. In addition to the 

 a smaller number of rays, delicate regular hexacts and sparsely 

 iinder the parenchymalia which lie outside the quadrate lattice- 

 ittes I found, near the external skin, some lophiohexasters with 

 fine, straight, perfectly parallel terminal rays, and I have also 

 tly unconnected oxyhexasters, but whether these belonged to this 

 sponge I was forced leave doubtful, though since then I have been led to regard this 

 as very improbable. 



The absence of ii oxyhexasters, as are so abundantly present in other Euplectellid 

 species, is very stril , and may perhaps be explained by the fact that the specimen in 

 question is very yo , as it seems to me not impossible that certain forms of spicules 

 only originate at ; mewhat late period. Such characteristic spicules as the thick 

 pentacts of Etq:)lec aspergillum, or the compass spicules of Enj)lectella oiveni, are at 

 any rate entirely a t from the cii'cular membrane surrounding the parietal apertures. 

 In the dermal s ton the delicate dagger-like hypodermal hexacts with a prolonged 

 proximal ray, whi' re so characteristic of the family of Euplectellidse, exhibit the 



id arrangement, and in most cases bear a floricome on the pro- 

 vIV. fig. 2). The floricome in no way difi"ers from that described 

 lum. On some of these hypodermal hexacts a bundle of freely 

 cts may be observed in place of the floricome (PL XIV. fig. 2). 

 ;uished by four prongs which project cross-wise in the middle, by 

 outer and inner ends, and by fine lateral teeth or prickles. These 

 lateral prickles arc >wever, sometimes absent (PL XIV. figs. 3, 4). The gastralia are 

 simple pentacts wit rolonged radial distal rays. 



As characteristic -eculiarities of this young sponge the following features may be 

 noted : — (1) the bunies of pointed diacts which project freely from the lateral wall and 

 are provided with mdian nodes ; (2) the three-toothed anchors of the longitudinal 



familiar connection 

 jecting distal ray ( 

 in Exiplectella aspi 

 projecting peculiar 

 These diacts are di 

 the sharp points on 



