PROTOZOA 153 



like some of the simplest plants. Indeed some of them are 

 claimed by both the botanists and the zoologists. It also seems 

 probable that the first animal life to appear on the globe had 

 the general characteristics of some of the Protozoa. Whether 

 some type of ancient protozoan is to be considered as the ances- 

 tor of the higher many-celled animals or not, it is true that we 

 find illustrated here in the simplest possible way the beginning 

 of all those functions which are so completely distributed among 

 the special organs of the complex animals. The Paramecium 

 does in a satisfactory way all that any complex living animal 

 needs to do in order to live and perpetuate its species. 



Fig. 67. Amceba. ec, ectosarc; «n., endosarc, containing food vacuoles (/); n, nucleus; p, pseudo- 

 podium; p-v., pulsating vacuole. 



Questions on the jfigure. — Define the various terms used in the legend above in 

 describing the parts of the amcfiba. What changes may the amoeba undergo in 

 its life history? Compare with figures 2 and 7. 



193. General Characters. 



1. Mostly unicellular throughout life. If colonial, all cells 

 similar and little or no division of labor. 



2. No true tissues or organs. 



3. The protoplasm usually consists of a clearer outer por- 

 tion {ectosarc) and a more granular inside portion (endosarc) 

 (Fig. 68, ec, en). 



4. Reproduction chiefly by fission, the resulting individuals 

 occasionally remaining associated. 



