1887.] NATURAL SCIENCES OF PHILADELPHIA. 175 



more gradually pointed. Their tliread-like fascicles form a compact 

 network. The gemmulai spicules are smooth, symmetrically bent 

 near each end, and form a thick layer around the gemmules ; but 

 are sparingly distributed through the tissues. The gemmuke have 

 a tolerably thick outer wall and are found everywhere in the 

 sponge." 



"Habitat : — Altrheini (?) near Eggensteiu, (in the vicinity of 

 " Karlsruhe). According to Prof. Niisslin, whom I thank for the 

 specimens, the sponge when living is green, and at all times can 

 be found on fascine bushes (Faschinen gestraeuch.'") 



Through the kindness of Prof. Eimer in Tiibingen, I was enabled 

 to examine a fragment of Euspongilla rhenana, and can offer some 

 additions to the description of Retzer. 



The gemmulae have the form and size of those of E. lacustris, but 

 the polar aperture (mikrodiode) is surrounded by a broad, plate-like 

 funnel. Upon the chitinous membrane is a very thin air-chamber- 

 layer consisting of 2-3 cells overlying one another. This layer was 

 rarely deeper than 5-6 cells in a column. The latter support the 

 greater number of spicules. They generally lie tangentially upon 

 the surface of the gemnuile and very few are embedded radially in 

 the air-chamber-layer. In sha])e these spicules are very variable, 

 and generally three principal forms can be determined. The most 

 {)lentiful are those which resemble the common skeleton spicules ; a 

 very few, those mentioned by Retzer, are bent double and such are 

 also scattered singly through the parenchyma ; finally, there are 

 found upon the surface of the gemnudse, spicules that are slightly 

 l)ent and compressed in the centre. 



The auxiliary a})ertures (neben-mikrodioden), numbering 3-6, upon 

 the surface of the gemmulse, are worthy of notice. About every 

 tenth gemmule has, near the principal aperture, some lateral fun- 

 nels ; which fact makes this form resemble the species described by 

 Carter from British Columbia, under the name of Spongilla midti- 

 poris. 



(b) Sub-gen. SPONGILLA, Wieizejski. 

 From 2-30 gemmulse as a rule, grouped in a conmion covering, 

 or placed pavement-like along side of one another. Mostly there is 

 a deep air-chamber-layer, through which smooth and rough spicules 

 are scattered. 



