PART III 



ANALYSIS OF BEHAVIOR IN LOWER ORGANISMS, 

 WITH A DISCUSSION OF THEORIES 



CHAPTER XIII 



COMPARISON OF BEHAVIOR OF UNICELLULAR AND MULTI- 

 CELLULAR ORGANISMS 



We have now examined the behavior of a number of Protozoa and 

 of a number of Metazoa. What characteristic differences do we find 

 between the two? 



This question is of interest from a number of points of view. The 

 Protozoa consist each of but a single cell, while the Metazoa are com- 

 posed of many cells, which are differentiated for the performance of 

 different functions. Does this difference in structure correspond to any 

 fundamental difference in behavior? Le Dantec (1895) proposed to 

 distinguish the life manifestations of the Protozoa as " elemental life " 

 from the life of the Metazoa, holding that the two are so different in 

 fundamental character that it is improper to apply the same name to 

 them; this point of view is often met in scientific literature. The life 

 of the Protozoa is considered " as the direct result of the diverse reactions 

 of a small mass of a certain chemical substance in the presence of appro- 

 priate substances " (I.e., p. 26), while that of the Metazoa is " the result 

 of the functioning of an extremely complicated machine, in which the 

 reactions of the chemical in question serve as motor power." The 

 former is compared to the burning of the alcohol in an alcohol motor, 

 the latter to the functioning of the motor itself (p. 27). We are inter- 

 ested in the question whether this theoretically fundamental difference 

 shows itself in any way in the phenomena to be observed. Is there any 

 objective evidence in the behavior for the belief that the life of the Pro- 

 tozoa differs fundamentally from that of the Metazoa? 



Again, the Metazoa possess a nervous system, while the Protozoa 

 have none. To the specific properties of the nervous system many of 

 the manifestations of behavior in higher animals have been attributed. 

 This system is often considered an essential prerequisite for certain 



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