32 



l)lOTyt)SrONGIl)/K. 



presence of certain spiculcis Hirailar to those which, in recent siliceous sponges, 



are found in the sarcode of the inner layer, is a reason for ascribing such 



layers to the Dictyosi'ongid-*:. 



To the dermal layer may be ascribed the umbrella-shaped clavules, or 



ambels, occuringin Cleodictya, Puysospongia and GiupiionicTYA (figures 6, 7) ; 



short, thick I'ods ^^ith an arched, 

 toothed disk at the end. To the 

 same layers, also, various forms of 

 the pinnies, some clearly pentac- 

 tin, others compound, among 

 them the peculiar tn'-p/'nuh/s 

 Avhich consists of three tufted 

 rays rising from a smooth base 

 with accessory processes (fig- 

 ixre 6). These pinnies have sel- 

 dom been found uiiliroken with 

 the exception of the tri-pinulus, 

 a form occiirring in Cleodicty'a 

 and Lebedictya. To the paren- 

 chyma (or perhaps to the quad 

 rules of the inner wall) may be- 

 long certain peculiar pentactins 

 with curved rays, found only in 

 Plirmjmodktya catiUiformis (fig- 

 ure 6 (1-4)) and the pod-shaped 

 diactins ^vhich occur in Phraomo- 



LeBEDICTYA, PlIYSO- 



FioDRE 6. Spicules of Dictyospongidae 



1, 2, 8, 4. Modified iiexactins of Phragmodictya catiUiformis. x 400. 

 6, 8, 7. Different forms of the pinuiug from Cleodictya Mohri. 

 X 400 ; 6 is a compiete tri-pinulus. 

 8, 9. Parts of ecliinate hexactins, also from Cleo. Mohri. x 400. 



10. Amuelimodifiedspicule fromCripAodicfyacjjfp/taiies. x 400. 



11. hn\imti»l\ PhyiospongiaColletti. x400. 



DICTYA, 



spongia, Gbiphodictya, etc., and 

 perhaps also, the highly branched 

 oxyhexasters characteristic of the genus Gripiiodictya (figiire 7). 



The prostalia or tufts of spicular rods occurring at the l)ase, aperture and 

 at various nodes upon the surface of some species, seem to penetrate the entire 

 wall and, in some instances, as in Hydnoceras and Piiysospongia, to bear a 

 definite relation to the intersections of the vertical and horizontal facicles of 

 the inner wall. 



Note. The terminology of the spicular elements of the s[)onges has in 

 recent years Ijecome very complicated through an exuberant growth of terms 

 Avhich do not explain themselves. The present profusion of names is quite 

 bewildering while the fundamental c<mception of the spicule form is 

 perfectly simple and the mode of its modification not of itself neccessaiily 



