File:Image from page 243 of "Introduction to zoology; a guide to the study of animals, for the use of secondary schools;" (1900) (14782692884).jpg

Identifier: introductiontozo00dave Title: Introduction to zoology; a guide to the study of animals, for the use of secondary schools; Year: 1900 (1900s) Authors: Davenport, Charles Benedict, 1866-1944 Davenport, Gertrude Anna Crotty, 1866- Subjects: Zoology Publisher: New York, Macmillan company London, Macmillian and co., ltd. Contributing Library: MBLWHOI Library Digitizing Sponsor: MBLWHOI Library

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Text Appearing Before Image: hat all Infusoria arederived from living germs. Whence the living germs come which enter the waterit is not difficult to determine. Many Infusoria can passinto a quiescent spore stage in which they may be driedand blown about without loss of life. Dry grass, straw,and other substances contain some of the germs, and othersfloat in the air and fall as dust into the water. Evendrinking water may contain here and there an infusorianor its germ. When, therefore, one fills a clean vesselwith pure water, and puts hay or dry leaves in it, and letsit stand open to the air in a warm place, the result ispretty sure to be that germs develop in the mixture.The heat and the organic infusion merely facilitate thisdevelopment. 224 ZOOLOGY Of all the Infusoria, none is more abundant than Para-mecium. It occurs everywhere, principally in stagnantfresh water, but also in salt water. It lives entirely onvegetable food, and is sure to abound wherever plantmatter is undergoing decay. When a culture is once

Text Appearing After Image: FIG. 207.—Carchesium, a stalked Vorticella. Greatly magnified. photograph of the living animals. From a started from a hay infusion, — which takes one or twoweeks, — it will be found to thrive especially on corn-meal.As an example of the Heterotricha, Stentor,1 the trumpet-animalcule, may be mentioned. Stentor is found attachedto vegetable debris — sticks, stones, water-weeds, and otherobjects — occurring in pools, ponds, lakes, and sluggishstreams. These things should be gathered and placed in 1 STTO>/>, a Greek at Troy, known for his loud voice. THE PAEAMECIUM AND ITS ALLIES 225 an aquarium, when the Stentors, if present, will attachthemselves to the glass sides of the vessel. The attach-ment of Stentor to objects is not permanent, for it mayloose its hold and swim free. When the animal is stainedin hcematoxylin, the characteristic nucleus, looking like achain of beads, becomes evident. Vorticella,1 the bell-animalcule, is found in pools orinfusions, perman

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