SPONGIAEIA 



81 



Fig. 138 — A, spicules of Spongilla lacustris; 

 B, gemmule of same (Siissw. F. Deut.). 



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

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

 species, G 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 

 fiesh-water sponge. 



S. fragilis Leidy. Sponge 

 not branching, growing in 

 flat patches, usually yellow 

 or brown but occasionally 

 green in color; gemmules 

 abundant, in one or more 

 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 (Mei/enia Carter). Gemmule with amphi- 

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



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

 color yellow^ or brown, sometimes green; needles smooth 

 or rough w^ith only the tip smooth; no smaller needles 

 present: cosmopolitan; in standing and running water, 

 preferring the former. 



3. Heteromeyenia 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 ra^'s 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 Avater. 



4. TuBELLA Carter. Discs of amphidisc of veiy unequal size, giv- 

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

 rounded tips: 5 species, 1 American. 



Fig. 139 — Ephj/dafia fluria- 

 tiUs. A, entire sponge attached 

 to a stick ; B, amphidiscs in 

 gemmule (Siissw. F. Deut.). 



