The animals and man; an elementary textbook of zoology and human physiology (1911) (14781651861)

Identifier: animansmanelemen00kell (find matches)
Title: The animans and man; an elementary textbook of zoology and human physiology
Year: 1911 (1910s)
Authors: Kellogg, Vernon L. (Vernon Lyman), 1867-1937 McCracken, Mary Isabel
Subjects: Zoology Physiology
Publisher: New York, H. Holt and company
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

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wo to four weeksabundant Amcebce are to be found on the surface of the sand and inthe scum on the sides of the tub; small Amcebce appear at first, andlater the large ones. Having found an Amoeba (fig. 12) note its irregular shape,and if it moves actively observe its method of moving. Howis this accomplished? The viscous, jelly-like substancewhich composes the whole body of an Amoeba is calledprotoplasm. The little processes which stick out in variousdirections are the false feet (pseudo podia). Note that theouter portion, the ectosarc, of the protoplasmic body is clear,while the inner, the endosarc, is more or less granular instructure. Has Amceba a definite body-wall? Do thepseudopodia protrude only from certain parts of the body? 37 38 THE ANIMALS AND MAN Within the endosarc note a clear globular spot which con-tracts and expands, or pulsates, more or less regularly. Thisis the contractile vacuole. Note the small granules whichmove about within the endosarc. These are food-particles
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FIG. 12. An Amoeba, showing forms assumed by a single individual infour successive changes. (Greatly magnified; from life.) which have been taken in through the body-wall. Note howpseudopodia flow about food-particles in the water and howthese are digested by the protoplasm. If an Amoeba comesinto contact with a particle of sand, note how it at onceretreats. Note within the endosarc an oval transparent body AMCEBA, PARAMCECIUM AND VORTICELLA 39 which shows no pulsations. This is the nucleus, a very com-plex little structure of great importance in the make-up ofA mceba. Note that Amceba has no mouth or alimentary canal; nonostrils or lungs, no heart or blood-vessels, no muscles, noglands. It is an animal body not made up of numerous dis-tinct organs and diverse tissues. Its whole body is a minutespeck of protoplasm, and forms a single animal cell. But ittakes in food, it moves, it excretes waste matter from thebody, is sensitive to the touch of surrounding objects, and,as we may be abl

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