THE SPONGES. 



41 





Whether 



longitudinally down into the sponge wall are unaccompanied by comitalia, 

 and with the exception of one case are not in intimate association with 

 particular principalia. In the case alluded to, Fig. 2, Plate 4, the tip 

 of the inferior ray is well overlapped by the two principal diacts of a 

 longitudinal skeletal bundle. There is but one case of anastomosis between 

 the bundles which are supported by the superior rays of the stauracts 

 (Fig. 2, Plate 4), and in only one of these bundles is there any evidence 

 of an existing or beginning transverse connection. This bundle bears a 

 laterally projecting small hexact (Fig. 2, Plate 4). 

 ends of the bundles, which are supported by the superior rays of the 

 stauracts, were connected in the living sponge, must remain an open ques- 

 tion. It may be added, however, that the upper margin of the sponge 

 and the surfaces of the bundles are smooth, and there is no indication in 

 the specimen itself that anything has been torn away. 



The marginal stauracts are 1.5 mm. to 3 mm. apart. The two rays 

 corresponding to the proximal and distal of the dermal hexact are reduced 

 to conical bosses. (This condition, instead of the pentact, is occasional in 

 R. phoenix according to Ijima, 1901, p. 271.) The superior ray is always 

 long, nearly cylindrical, tapering eventually to a point, smooth or with a 

 surface made undulating by scattered low and rounded tubercles. The 



■ 



three other rays are smooth and taper gradually to a point. They vary 

 greatly in absolute and relative lengths. The inferior ray may be the 

 longest or much the shortest of the four developed rays. The lateral rays, 

 lying parallel to the sieve-plate margin, may be equal or unequal in length, 

 and very much shorter than or nearly as long as the superior ray. In the 

 largest spicules the superior ray is 4.5 mm. to 4.8 mm. long and 250 /x to 

 300 /u, thick at the base; the other rays having about the same basal 

 thickness. Two of the marginal stauracts, one of which is shown in Fig. 7, 



— 



Plate 3, are much smaller than the others, the superior ray measuring 

 about 2.4 mm. x 120 /x. The marginal stauractines, it will be seen, are 



small as compared with the 



larger of 



the corresponding spicules in 



M. phoenix (Ijima, 1901, p. 272, gives the combined length of the superior 

 and inferior rays as reaching 30 mm.), and the rays vary more in relative 

 length than in the spicules examined by Ijima. 



The thickened margin representing the cuff of some other species is a 

 band about 1 mm. wide. It consists chiefly of closely packed diacts, mostly 

 slender forms 10 to 30 xt thick, with some larger ones up to 60 /x thick, 



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