210 ART. 7. T. TJIMA : IIEXACTINELLTDA, IV. 



else than old and much lacerated, anchoring needles of a Hyalo- 

 nema species, — presumably, of //. affine. The ends of the needles 

 are invariably broken ; some of them show the characteristic 

 spines on the surface ; and their surface, so for as it lies imbedded 

 in the sponge, is covered with a thin siliceous reticulum, the 

 same as the so-called basal-plate which is known to develop on 

 the attachment surfece of so many Hexactiuellids firmly fixed to 

 the substratum. It is then beyond dispute that the S. glaber 

 in question had attached itself to, and was growing on, a tuft of 

 Hyalonema needles. 



Another very interesting fact in relation to the specimen 

 under consideration is tlie presence in large numbers of certain, 

 peculiar, small bodies lodged among the tissues of the choanosome. 

 To these bodies I have already had occasion to refer in Contrib. 

 I. (p. 186, foot-note) of this series of Studies. To the naked 

 eye they appear as whitish spots of various sizes under 0.6 mm. 

 diameter. Except in the ectosome and the endosome, they occur 

 throughout the sponge in tolerably uniform distribution. Under 

 the microscope the body is found to be a reticular mass of no 

 definite shape ; it consists of an irregular rigid framework of 

 microtuberculate siliceous beams (PL XV., fig. 13). The mass is 

 always traversed quite through by a few parenchymal diactins of 

 the sponge containing it. It is further easy to make out that 

 the aforesaid beams are formed by the solderins; t02;ether of small 

 but comparatively thick-rayed hexactins that exhibit no regularity 

 as to their relative disposition. The hexactins (under 100 ,« in 

 length, and 10 n in thickness, of rays) are in characters quite 

 similar to those that go to comj)Ose the basidictyonal framework 

 of the species (see PI. XV., fig. 12). In fact, I have no hesita- 

 tion in regarding the above described reticular bodies to be the 



