. Beginners' Zoology . Protozoans furnish a large amount of food to the higheisniraals. CHAPTER III SPONGES Suggestions.—In many parts of North America, fresh-watersponges may, by careful searching,be found growing on rocks and logsin clear water. They are brown, creamy, or greenish in colour, and re-semble more a cushion-like plant than an animal. They have a char-acteristic grittv feel. They soon die after removal to an aquarium. A number of common small bath sponges may be bought and keptfor use in studying the skeleton of an ocean sponge. These spongesshould not have largeholes in the bott
. Beginners' Zoology . Protozoans furnish a large amount of food to the higheisniraals. CHAPTER III SPONGES Suggestions.—In many parts of North America, fresh-watersponges may, by careful searching,be found growing on rocks and logsin clear water. They are brown, creamy, or greenish in colour, and re-semble more a cushion-like plant than an animal. They have a char-acteristic grittv feel. They soon die after removal to an aquarium. A number of common small bath sponges may be bought and keptfor use in studying the skeleton of an ocean sponge. These spongesshould not have largeholes in the bottom; ifso, too much of thesponge has been cutaway. A piece of marinesponge preserved in alco-hol or formalin may beused for showing thesponge with its flesh inplace. Microscopic slidesmay be used for showingthe Fig. 21. — Fresh-water Sponge. The small fresh-watersponge (Fig. 21) lacksthe more or less vase-like form typical of sponges. It is a rounded mass growingupon a rock or a log. As indicated by the Arrows, where does water enter the sponge? Thismay be tested by putting colour-ing matter in the water nearthe living sponge. Where does\\\Q. water come oiitl {V\g. 23.)<cc. .^,^x, ec \ ; Does it pass throtigh ciliated -Section of fresh-water sponge ^ t (enlarged). chaml?ers in its course ? Is the c 17
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