Chapter 4 

 Physiology 



THE morphological consideration which has been given in the 

 last chapter, is, though necessarily brief, indicative of the oc- 

 currence of various and often complex organellae in Protozoa. 

 The physiological activity of the whole protozoan is the sum-total 

 of all the functions which are carried on by numerous minute 

 parts or organellae of the cell body, unlike the condition found in 

 a metazoan. Indeed, as Calkins (1933) stated, "physiological 

 problems (of Protozoa) for the most part begin where similar 

 problems of the Metazoa leave off, namely the ultimate processes 

 of the single cell. Here the functional activities have to do with 

 the action and interaction of different substances which enter into 

 the make-up of protoplasm and, for the most part, these are be- 

 yond our powers of analysis." A full discussion of various physio- 

 logical problems pertaining to Protozoa is out of question in the 

 present work and, therefore, a general consideration on protozoan 

 physiology will suffice for our purpose. 



Nutrition 



The Protozoa obtain nourishment in manifold ways, which 

 may be placed under three types: holozoic, holophytic, and sapro- 

 zoic. 



Holozoic (zootrophic, heterotrophic) nutrition. This is the 

 method by which all higher animals obtain their nourishment; 

 namely, the protozoan uses other animals or plants as sources of 

 food. It involves the food-capture and ingestion, the digestion 

 and assimilation, and rejection of indigestible portions. 



The methods of food-capture vary among different forms. In 

 the Sarcodina, the food organisms are captured and taken into the 

 body at any point. The methods however vary. According to 

 Rhumbler's oft-quotied observations, four methods of food-inges- 

 tion occur in amoebae (Fig. 32) ; namely, 1) by "import," in which 

 the food is taken into the body upon contact, with very little 

 movement on the part of the amoeba (a); by "circumfluence," in 

 which the cytoplasm flows around the food organism as soon as it 

 comes in contact with it on all sides and engulfs it (b); 3) by "cir- 



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