Chapter 4 

 Physiology 



THE morphological consideration which has been given in the 

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

 rence 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 inter- 

 action of different substances which enter into the make-up of 

 protoplasm and, for the most part, these are beyond our powers of 

 analysis." A full discussion of various physiological problems per- 

 taining to Protozoa is out of question in the present work and, there- 

 fore, a general consideration on protozoan physiology will suffice 

 for our purpose. 



Nutrition 



Protozoa obtain nourishment in manifold ways. Information on 

 the nutrition of the Protozoa is undergoing an accelerated progress 

 through improvements in technique in experimental cultivation. In 

 many Phytomastigina (Pringsheim, 1937a; Hall, 1939), afewciliates 

 (Kidder and Dewey, 1951) and many blood-inhabiting flagellates 

 (Lwoff, 1951) which have been cultivated in vitro free from other 

 organisms, a much clearer information is becoming available. But 

 for the majority of Protozoa a thorough comprehension of the nutri- 

 tion is to be sought in future (Doyle, 1943; Lwoff, 1951; Most, 1951; 

 Kidder, 1951). 



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, digestion and assimilation, and re- 

 jection 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 

 (1910) oft-quoted observations, four methods of food-ingestion oc- 

 cur in amoebae (Fig. 33) ; namely, (1) by "import," in which the food 

 is taken into the body upon contact, with very little movement on 



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