The royal natural history . Esperiqp&is challengeri (h nat. size). 544 SPONGES. Fresb-Water To the group under consideration belong the fresh-water sponges sponges. (Spongillidoe), which live in ponds, canals, lakes, and rivers all overthe world ; and have been known to infest the pipes supplying a city with two commoner British species (Euspongilla lacustris and Ephydatiafluviatilis)grow on the piles of bridges, the sides of locks, the stems of water-weeds, orform crusts on the bed of rivers. Euspongilla forms bright green crusts, fromthe surface of which long, simple, or branched s
The royal natural history . Esperiqp&is challengeri (h nat. size). 544 SPONGES. Fresb-Water To the group under consideration belong the fresh-water sponges sponges. (Spongillidoe), which live in ponds, canals, lakes, and rivers all overthe world ; and have been known to infest the pipes supplying a city with two commoner British species (Euspongilla lacustris and Ephydatiafluviatilis)grow on the piles of bridges, the sides of locks, the stems of water-weeds, orform crusts on the bed of rivers. Euspongilla forms bright green crusts, fromthe surface of which long, simple, or branched stems arise ; or the surface of thecrust may be simply conulated. This green colour is due to granular bodies whichcrowd the cells near the surface of the sponge. Some naturalists consider thesebodies to be chlorophyll granules similar to those of plants ; others regard them assingle-celled algre. The chlorophyll, in the presence of sunlight and water, splits. LIMESTONE BORED BY SPONGE. up the carbonic acid evolved by the sponge into carbon and oxygen, the latterbeing used by the sponge for respiration. Fresh-water sponges growing in shadyplaces are of a pale grey or yellowish white colour; and when bright greenspecimens are kept in the dark, they lose their green colour. The surface ofa fresh - water sponge is covered with fine pores, while here and there a fewlarge oscules are visible. From the pores fine in-current canals pass down to theflagellated chambers, and from the latter proceed the rootlets of the out-currentcanal-system. With a lens the spindle-shaped siliceous spicules of the skeleton canbe made out. They are about one-fiftieth of an inch in length and unite in bundleswhich partly surround the canals, and are partly scattered irregularly in the groundsubstance ; with the naked eye the bristling points can be seen projecting fromthe surface. If a specimen be examined in autumn, there will generally be foundcrowding the meshes a
Size: 2027px × 1233px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, booksubjectnaturalhistory, booksubjectzoology
