CHAPTER I 



PROTOZOA 



In commencing the study of Zoology it is advisable to do so by making 

 a study in some detail of one particular type of animal^ so as to obtain 

 definite and precise data to serve as a foundation for further knowledge. 

 It is also desirable to select as the object of this study some animal 

 possessing the minimum complexity of structure so that the beginner 

 may easily grasp from it what are the fundamental features of animal 

 organization. 



Such a creature is the little animal called Amoeba proteus which is to 

 be found still surviving on the Earth to-day, as a not uncommon inhabitant 

 of freshwater pools and slowly moving streams, although it represents a 

 relatively very early stage in the evolution of animal life. 



Amoeba proteus 



The Amoeba consists of a minute particle just visible to the naked 

 eye — measuring up to about "6 mm. in diameter — of that substance or 

 mixture of substances which we call protoplasm and which Huxley used 

 to speak of as the " ph)'sical basis of life " — because the condition which 

 we call life occurs, so far as we know, only as an attribute of this substance. 

 Wherever you find life there you find protoplasm. It would be of course of 

 tremendous interest to obtain exact knowledge of the chemical and physical 

 constitution of protoplasm because once this knowledge was obtained it 

 would be but a comparatively small step farther to produce protoplaS^ri— ^to 

 make it in the laboratory. But unfortunately this knowledge ha? eluded — 

 and probably must for ever elude— discovery, for the very first steps in 

 the investigation — ^the first steps of chemical analysis — ^are such that they 

 deprive the protoplasm of its all-important characteristic — that 6i livii^g 

 — the property which marks it off from all other substances. 



It is naturally of interest, though of relatively minor interest, to 



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