. The life of inland waters; an elementary text book of fresh-water biology for American students. Freshwater biology. 164 Aquatic Organisms quent detachment, they become numerous when plancton abounds. Kofoid ('08) found a maximum ntimber of 5335 hydras per cubic meter of water in Quiver Lake during a vernal plancton pulse in 1897. Fresh-water sponges grow abundantly in the margins of lakes and pools and in clear, slow-flowing streams. They are always sessile upon some solid support. In sunlight they are green, in the shade they grow pale. The species that branch out in slender finger-like pr
. The life of inland waters; an elementary text book of fresh-water biology for American students. Freshwater biology. 164 Aquatic Organisms quent detachment, they become numerous when plancton abounds. Kofoid ('08) found a maximum ntimber of 5335 hydras per cubic meter of water in Quiver Lake during a vernal plancton pulse in 1897. Fresh-water sponges grow abundantly in the margins of lakes and pools and in clear, slow-flowing streams. They are always sessile upon some solid support. In sunlight they are green, in the shade they grow pale. The species that branch out in slender finger-like pro- cesses are most suggestive of plants in both form and color, but even the slen- derest sponge is more massive than any plant body; and when one looks closely at the surface he sees it rough- ened aU over with the points of innumerable spicules, and sees open osteoles at the tips. By Fig. 74. Three simple metazoans of thcSC SlgnS SpOUgCS of isolated structural types. t, + r i j4, a scruff back, Ckalonotus; B, Hydra, bearing a WJiateVer lOmi Or COlOr bud; c, a tardigrade. M<.«.o6 ^^.g easily recoguized. The commonest sponges are low encrusting species that grow outspread over the surfaces of logs and timbers. When, in early summer, one overturns a floating log that has been long tindisttubed he may find it dotted with young sponges, growing as little yellow, circular, fleshy discs, bristling with spicules, and each with a large central osteole. Later they grow irregular in outline, and thicker in mass. Toward the end of their growing season they develop statoblasts or gemmules (winter-buds) next to the substrattmi (see fig. 00 on p. 00), and then they die and disintegrate. So our fresh-water sponges are creatures of summer, like Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Needham,
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectfreshwa, bookyear1915
