172 M. H. Fol on the 



may be readily distinguished from either by its elongated 

 snout, which allies it to the four species first mentioned. Of 

 these, >S'. laticaudatus is separated by its larger size, shorter 

 hair, browner colour, nearly white belly, and still longer 

 muzzle ; S. rujigenis by the brilliant rufous of its cheeks and 

 the underside of its tail ; 8. Pernyi by its similarly rufous 

 tail ; and S. Berdmoreihy the black and white longitudinal 

 stripes with which its body is ornamented. No other species 

 that I can find have any close relationship to the new form 

 discovered by Mr. Everett, in whose honour I have very 

 great pleasure in naming it. 



XXI. — On the Anatomy of Horny Sponges belonging to the 

 Genus Hircinia, and on a new Genus. By H. FoL*. 



The genus Hircinia was created by Nardo in 1833 for 

 certain horny sponges possessing two systems of fibres — some 

 coarse and analogous to those of the bath-sponge {Euspongia), 

 and others very fine and numerous, resembling the elastic 

 fibrillse of the connective tissue of Vertebrates. The structure 

 of these fibrillae was investigated by Lieberkiihn, O. Schmidt, 

 and F. E. Schulze, who showed that they do not anastomose, 

 but terminate in all directions in rounded swellings. The 

 two latter authors, however, like KoUiker and Hyatt, con- 

 sidered that these fibrils probably belonged to a parasite or to 

 a commensal of these sponges. It was for this reason that 

 the family Filiform was actually abandoned ; so that Vos- 

 maer, in his monograph of the Spongiarite, does not recognize 

 a single genus belonging to this family, and suppresses it. 



Sections which I have made of specimens of Hircinia 

 variabilis and Hircinia sp. n., from the neighbourhood of 

 Nice, have enabled me to solve the disputed question of the 

 origin and nature of the fibrillffi, and this in a sense opposed 

 to that of recent authors. 



On making a series of somewhat thick transverse sections 

 of a specimen macerated for a few hours only, so as to sepa- 

 rate the epithelia while leaving the connective tissue un- 

 touched, we see at once in the clearest possible way that the 

 fibrils are not disposed at random, as would be the case were 

 we dealing with a parasite, but form a system of incomplete 

 septa, which alternate with the fibres of the skeleton, with 



* Translated from tlio ' Coiuptos Roiidus des Si5auce3 do I'Acad^mie 

 des Scieuces,' tome ex., June 9, 1690, p. 1:?09 et seij. 



