SPONGIAEIA 



81 



1. SPONGILLA Lamarck. Gemmule without amphidiscs, but sur- 

 rounded by needles or rods alone; large needles usually smooth: 17 

 species, 6 American. 



S. lacustris (L.) (Fig. 138). Sponge branching and usually green, 

 with smooth longer (megascleres) and rough shorter (microscleres) 

 needles; gemmules surrounded by spiny curved rods, but occasionally 

 without them, and often scarce until late in the fall: cosmopolitan, pre- 

 ferring running water and 

 sunlight ; the commonest 

 fresh-water sponge. 



S. fragilis Leidy. Sponge 

 not branching, growing in 

 flat patches, usually yellow 



or brown but occasionally 

 green in color; gemmules 



A 6 



abundant, in one or more ^g. 



layers at the base of the 



sponge; large needles smooth; no microscleres in body of sponge: in 



standing and running water and avoiding the light; next to the above, 



the commonest species. 



2. EPHYDATIA Lamouroux (Heyenia Carter). Gemmule with amphi- 

 discs all of one type: 17 species, 8 American. 



E. fluviatilis (L.) (Fig. 139). Sponge massive, occasionally lobate; 

 color yellow or brown, sometimes green; needles smooth 

 or rough with only the tip smooth; no smaller needles 

 present: cosmopolitan; in standing and running water, 

 preferring the former. 



3. HETEEOMEYENIA Potts. Similar to 

 Ephydatia, but the gemmule has amphidiscs 

 of two different types, the less numerous 

 being much longer than the other and with 

 long hooked rays on the discs : 3 species, all 

 American. 



H. ryderi Potts. Sponge massive, 

 often hemispherical, lobed, light green in 

 color; needles rough, except at the tips; long amphidiscs with spiny 

 shaft and discs consisting of 3 to 6 recurved hooks; short amphidiscs 

 with usually smooth shaft and large flat discs: eastern and central 

 North America, in shallow-flowing water. 



4. TTJBELLA Carter. Discs of amphidisc of very unequal size, giv- 

 ing it the shape of a collar button; needles rough, sometimes with 

 rounded tips: 5 species, 1 American. 



Fig. 139 Ephydatia fluvia- 

 tilis. A, entire sponge attached 

 to a stick ; B, amphidiscs in 

 gemmule (Siissw. F. Deut). 



