. Civic biology; textbook of problems, local and national, that can be solved only by civic coöperation. Biology. Ui ribll \Mj ii.^ lUu'i food; that is, if they were thriving and growing, iliuy winUd resist attacks of saprolegnia or other disease germs. A variety of plants and animals is essential in a halancctl {mukI it" it is to snpply food continuously to all its inhal)itants. As with similar pi'ohlems on land, the most necessary tiling is an abundance of {)lants, to sui)ply food for snails, mussels, in- sects, worms, Crustacea, and vegetable-feeding lishcs; muss
. Civic biology; textbook of problems, local and national, that can be solved only by civic coöperation. Biology. Ui ribll \Mj ii.^ lUu'i food; that is, if they were thriving and growing, iliuy winUd resist attacks of saprolegnia or other disease germs. A variety of plants and animals is essential in a halancctl {mukI it" it is to snpply food continuously to all its inhal)itants. As with similar pi'ohlems on land, the most necessary tiling is an abundance of {)lants, to sui)ply food for snails, mussels, in- sects, worms, Crustacea, and vegetable-feeding lishcs; mussels should be present in sullicient numbers to strain ont any excess of floating alga? and fungi: and, Hnally, there nuist be enough carnivorous forms to prevent exces- sive nuiltiplication of the vegetarians. Of course this natural bal- ance of lakes and ponds is a more complex mat- ter than tliat of our aquaria, since these are never required to pro- duce all the foods of the ^^^ 9. 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 Hodge, Clifton Fremont, 1859-; Dawson, Jean, 1873-. Boston, Ginn
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Keywords: ., bookleafnumber327, bookpublisherbostonginn, booksubjectbiology
