23S A>[rEBA CHAP. 



marked, some cells giving rise to organs of locomotion, 

 others to organs of reproduction, and so on. ]!ut every 

 function necessar)' for the life of an animal — or a plant — is 

 due in the first instance to protoplasm, and a simple cell, 

 like the Amceba, can perform them all. 



In the next two chapters we shall study certain other 

 unicellular organisms which show an advance on Amceba in 

 possessing a certain amount of morphological and physio- 

 logical differentiation. But the structural differentiations, as 

 they are merely parts of one cell, cannot be spoken of as 

 "organs" in the sense in which we have used the word 

 hitherto, as they are not composed of numerous cells. 

 'I'hey are, however, organs in the physiological sense, as 

 they perform different functions. 



I'R.VCTICAL DIIiECTIONS.i 



Amoeba. 



J'^xaniinc a (lrr)p of water containing Amoeba?, front the bottoni of a 

 pond, with the low power, first putting on a cover-glass : if the water 

 does n<^>t contain snrali pai tides of sand or niud, place a small piece of 

 paper under the edge of the cover so as to avoid crushing the organisms, 

 When you have found a specimen, put on the high power, and note — 

 • I. The irregular and c/iaiig-ing form o{ the animal, the protopla.sm 

 running out \nU>\>\\.mi pseiidofods. 



^. The granular character of the prot(iplasm, the granules usnally 



^ \'ou should, if possible, try and oljtain specimens of Amceba:; and 

 the other fresh-water organisms described in this and the two following 

 chapters for yourself, by collecting stagnant pond-water, together with 

 a little of the mud at the Ijottom and some water-w eeds, and letting 

 it stand for a few days in a glass jar or bottle. If you are unable to 

 fmd tlie organisms you require, they, as well as most of the other 

 animals ilescribed in this book, may be obtained from dealers in 

 Natural History objects (see e.^. the advertisements in Nalurc). 



