4.6 THE EVOLUTION OF MAN. 



organic phenomena of life, of nutrition, reproduction, sensa- 

 tion, and movement. If we tried to construct, a priori, the 

 simplest conceivable organism, we should always be com- 

 pelled to fall back upon such a Monera. 



Although in all real Monera the body consists merely 

 of such a small living piece of plasson, yet, among the 

 Monera, which have been observed in the sea and in 

 fresh water, we have been able to distinguish several dif- 

 ferent genera and species, varying in the mode in which their 

 tiny bodies move and reproduce. In the ways in which 

 movement is accomplished very noticeable differences exist. 



Fig. 163. — A Moneron (Protamoeba) in the act of reproduction : A, the 

 whole Moneron, which moves, like the ordinary Amoeba, by means of variable 

 processes ; B, a contraction round its circumference parts it into two halves ; 

 C, the two halves separate, and each now forms an independent individual 

 (much enlarged). 



In some Monera, especially in the Protamoeba (Fig. 163), 

 the formless body, during its movements, invariably de- 

 velops only a few, short, and blunt processes, which project 

 like fingers, slowly altering their form and size, but never 

 branching. In other Monera, on the other hand (e.g., 

 Protomyxa, Myxastrum), very numerous, long, fine, and 

 generally thread-like processes arise from the surface of 

 the movable body, and these branch irregularly, inter- 



