PORIFERA. III. 



i. H. Ingolfi n. sp. 



PI. II, Figs. 14, PI. IV, Fig. 4. 



Of someiv hat various shape, more or less roundish with a number of tubifonn fistula which may 

 be branched; or of more irregular shape, showing several swellings or finally quite without swellings ; 

 growing freely without attachment. Surface smooth. Outermost a solid, bladder-like dermal layer. Oscula 

 at the summit of some of the fistiila, (pores at the summit of others?). The skeleton of the dermal 

 layer formed of close-lying spicules parallel -with the surface; the inner skeleton consisting of fine, 

 irregularly winning fibres, which are reg^^larly arranged at the surface parallel with this, without trans- 

 verse fibres. Spicula: megasclera of two forms, tylota (729 0-65""", acanthoxea o-ij 0-21""*; microsclera 

 two forms, chela arcuatce 0-021 0-028""*, sigmata 0-056 0-06 i mm . 



This species in its exterior shape somewhat recalls Plistoderma appcndiculatiim , but it is 

 generally less regular. Most frequently it consists of a more or less roundish body with a varying 

 number of tube-shaped appendages. These appendages or fistulse may vary much in length and 

 thickness, and there are often, besides the larger, also some short and thin fistulse; these may 

 be branched in different ways, and they may be more or less curved; the appendages also may 

 form swellings, the sponge in this case consisting of more than one roundish swollen part connected 

 by the appendages. Finally there are specimens which have no pronounced swelling, or no swelling 

 at all, the sponge then consisting of a somewhat sinuous, slightly branched tube of somewhat different 

 thickness in different places. In the largest specimen the body has a diameter of fully 20 mm , the 

 longest fistula has a length of 42""" and its thickness is 4 mm ; then we have specimens in all sizes 

 down to quite small, the smallest one has a body with a diameter of 2-5 mm and a fistula of a length 

 of 14 mm and a thickness of 1-7 n. The sponge grows freely without any attachment. The colour (in 

 spirit) is yellowish white. The consistency is somewhat bladder-like, the outer layer is hard and firm, 

 the inner body brittle, the latter is as usually highly contracted, so that it only occupies a small 

 part of the cavity within the dermal rind. The surface is mainly smooth, yet the ends of the tangential 

 spicules of the dermal layer may sometimes be a little projecting. The sponge is outermost sur- 

 rounded by a solid and hard dermal layer, formed of close-lying spicules, the layer has a thickness of 

 about o-2 mm . Oscula and pores: A part of the fistulse are distinctly seen to be oscular fistulse, they 

 terminate with a simple opening, or they are in most cases more or less closed and terminate in 

 a conically pointed part which is either quite closed or shows an opening at the summit. Pores I 

 have not observed, but they are certainly placed at the end of some of the fistulse; in my material 

 however the outer part of these is often broken off; at all events pores are not found otherwise on 

 the body. The inner body is in nearly all specimens strongly contracted or quite destroyed, yet in 

 some single specimens it may be seen to have had a surface as in Histoderma appcndiciilatuin, with 

 pores leading into canals; the direction of the water-current therefore is probably the same as in that species. 

 The skeleton. The dermal skeleton; the skeleton of the dermal layer is constructed as in //. 

 appendiculatum ; it consists of close-lying tangential spicules in several layers, the spicules are more 

 or less circularly arranged around the bases of the fistulse, and here likewise, especially on the 

 inside of the layer, we find spicules which lie at right angles to the others, these latter spicules 



