186 PROCEEDINGS OF THE ACADEMY OF [1887. 



their shade, killed by the too abundant Avater, now stand gaunt 

 and desolate above it, "bearded Avith moss" that hangs and flutters 

 from their otherwise naked branches. 



At many places in this beautiful pond the fallen timbers, water- 

 logged at depths of three to six feet, are lined for yards with this 

 sponge ; sometimes only as a smooth, green, enveloping sheet, but at 

 other places reaching out long, radiating branches for six inches or 

 more, swayed delightfully by the clear current. Not only in the 

 "perfect days" of June or through the heats of mid-summer, is the 

 sponge thus verdant and thrifty ; but when December has robbed 

 the lake of most of its vegetable forms, — even after February has 

 for weeks covered it with a thick sheet of ice, the sponge has been 

 seen still green and apparently in as healthy growth as ever. 



Concurrently Avith this evergreen habit, we notice the unusual 

 scarcity of gemnudes at all times of the year, and feel warranted in 

 inferring that, gifted as it is Avith this ability to with-stand a low 

 temperature in its growing state, it does not need to form "protected 

 gemmules" to conserve its life during hybernation. 



In the microscopical study of S. aspinosa, the distinctive feature 

 is, undoubtedly, the presence upon the dermal film and amongst 

 the generally smooth, slender, skeleton spicules, of great numbers of 

 minute smooth acerates. These are not altogether uniform in size, 

 however; and enough of ati intermediate character are occasionally 

 seen, to suggest the possibility that they may be merely initial and 

 immature conditions of the skeleton spicules. The continued per- 

 ennial groAVth of the sponge, makes this supposition the more probable; 

 as there is no season in Avhich, as in the case of most other sponges, 

 it may be said to have reached maturity or completeness. In some 

 preparations of it, aborted forms of skeleton spicules are foimd in 

 considerable numbers and spherical or discoidal masses of silica, 

 without spinous prolongations, or Avith but a single spine, are not 

 infrequently met Avith. 

 (2) Spongilla lacustris, Linn. (PJ. V, fig. 1; PI. VII.) 



"Branched; branches long, round and sharp-pointed. Color dark 

 brown, structure fibrous. Skeleton spicule curved, fusiform, grad- 

 ually sharp pointed, smooth; sometimes more or less spiniferous. 

 Flesh spicule thin, curved, fusiform, gradually sharp-pointed, spiued 

 throughout. Statoblast Avhen fully developed globular ; crust com- 

 posed of granular cell-structure, charged with more or less curved, 

 minute, stout, fusiform, sharp pointed acerates, covered with stout 



