ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 613 



2. Sycon-tj-pe, the secondary form ; the part which bears the 

 collar-cells opens into the gastral cavity, and this alone opens to the 

 exterior. 



3. The tertiary form is represented by Aplysilla, Spongelia, 

 Halisarca Dujardini, Leucandra aspera, most Benierida, some Suheri- 

 tida, and probably the Hexactinellida. Plakina is on the border of 

 this group. The part which bears the collar-cells opens directly into 

 wide canals, and these in turn into broader vessels, or into the gastral 

 cavity, which opens directly to the exterior. 



4. The quaternary, the most differentiated form, finds numerous 

 representatives among the horny and siliceous sponges. Lowest 

 come Aplysina, Euspongia, Cacospongia, Hircinia, Oligoceras, PlaJcortis, 

 Plakinastrella ; higher stand Halisarca lobularis (which, by reason 

 of its great differences from R. Dujardini, Vosmaer proposes to dis- 

 tinguish generically as Oscaria), Chondrosia, Chondrilla, Corticium 

 candelabrum. The part which bears the collar-cells does not open 

 directly into wide excretory canals, but by the medium of tubes, 

 usually very fine. The actual point of entrance of the inhalent canal 

 into the ciliated chamber is termed the pore, in preference to usual 

 application of this term to the opening at the surface of the sponge. 



New Fresh-water Sponges.* — Mr. E. Potts records several new 

 species of Spongillce which give reason to believe that the order 

 Spongida has many more fresh-water representatives than has been 

 generally supposed. 



The first, Spongilla tenosperma, exhibits features so exceptional as 

 almost to claim for it generic distinction. It was found in a small 

 stream near Philadelphia creeping upon and around Anacharis and 

 willow roots, matting them together, and thus forming loose irregular 

 masses several inches in diameter ; colour yellowish, light or dark 

 green, according to exposure to the light. Sphserulse globular, light 

 yellow or brown, rather numerous amongst the roots and spicula; 

 covered with long birotulate spicula radially arranged; foramen 

 elongated into a tube flaring at its extremity and dividing into 2-5 

 tapering, slender, curling or twisted tendrils, believed to be as much 

 as half an inch in length. The sarcode decomposes early in the 

 season, and most of the skeleton spicula are then washed away ; but 

 these tendrils hold the mass of sphserul^ attached to the roots, &c., 

 above mentioned, awaiting the spring germination. 



In the same place a variety was found resembling S. lacustris in 

 its general appearance and in the shape of its skeleton and dermal 

 spicules, but differing in that the seed-like bodies or sphaerulse are 

 entirely smooth, showing no incrustation of curved spined spicula as 

 in the European species. 



A very slender green species was also found creeping along stems 

 of Sphagnum, &c., in a swamp near Absecom, N.J. As it appeared to 

 be entirely without spined spicula of either class, the name proposed 

 for it is S. aspinosa. 



In the Adirondack lakes a beautiful species, believed to be iden- 



* Proc. Acad. Nat. Sci. Phik., 1880, pp. 330-1 and 356-7. 



