f -Al ) 



einander anostomosiren, so dass hier ein engmasschiges, spongioses 

 Netz zu Stande kom rat. In einigen der Knotenpunkte dieses Fadennetzes 

 liegen die Zellleiber mit ihrera kngligen Kern, in anderen trifft man 

 nur unbedeutende Plasmaanhaufungen an." In my MS. description 

 of this tissue in Clionidae I differ somewhat from Lendenfeld's 

 interpretation; in Poterion I find the same sort of tissue, only still 

 more pronounced. The fact is that the reticulum is by no means 

 simply formed by a network of "Auslaufer" of cells, as it becomes 

 clear by careful focussing that a number of the supposed thread- 

 like processus are really membranes. In Poterion these membranes 

 are sometimes of enormous size, even larger than in Cliona {Osculina). 

 The tissue has a close resemblance to the so-called lymphoid or 

 reticular tissue, as Ranvier and Pekelharing conceive it. 



As to the skeleton of Poterion, this is formed by a trabecular 

 very firm network of bundles of closely packed tylostyles. I found 

 in Osculina that in some portions of the skeleton the spicula were 

 united by a little spongin. The same holds true for Poterion. This 

 is, however, only the case in the centre of the pillars or trabeculae; 

 there is a mantle of spicules at the periphery which is devoid of 

 spongin. The spicula of Poterion are tylostyles; the spicule for which 

 I proposed l ) the name spinispira I did not find in the specimens of 

 Poterion I examined. We know, however, that in the genus Cliona 

 itself spinispirae are often very rare or absent, especially in the 

 so-called free stage. I am of opinion that Papillina suberea O.S. is 

 identical not only with Osculina polgstomella O.S., but also with 

 Papillina nigricans O.S. and Vioa viridis O.S. They are all nothing 

 but modifications of the very variable Cliona celata, as I hope to 

 prove in my "Sponges of Naples". Lendenfei.d (1897 I.e. p. 99) 

 considers Papillina suberea O.S. as a species different from Papillina 

 nigricans O.S. This is especially on account of the absence of 

 spinispirae in the former, in a type-specimen of which Lendenfeld 

 failed to find them. I found, however, in the collection of the 

 Zoological Station at Naples a sponge labelled by Schmidt P. suberea ; 

 in this specimen I did find spinispirae. I found them likewise in 

 some of the specimens I collected near Trieste. For these reasons 

 I cannot distinguish nigricans from suberea. Consequently there is 

 in the absence of spinispirae in Poterion no ground for not placing 

 this sponge in the same group as Cliona, since in every respect 

 the anatomical structure of Poterion resembles that of Osculina. 



Legden, May 14, 1908. 



l ) On the shape of some Siliceous Spicules of Sponges. (Kon. Akad. v. Wetensch. 

 Amsterdam, 1902. Proceedings p. 104—114). 



