152 ZOOLOGY 



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 protozoan is to be considered as the ancestor 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 simple yet satisfactory way all that any complex living 

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



FIG. 67. Amoeba, ec., ectosarc; en., endosarc, containing food vacuoles (/); n, nucleus; p, pseudo- 

 podium; p.v., pulsating vacuole. 



Questions on the figure. Define the various terms used above in describing 

 the parts of the amoeba. What changes may the amoeba undergo in its life history ? 

 Compare with figures 2 and 7. 



193. General Characters. 



1. Mostly unicellular throughout life. May have one or 

 more nuclei (Figs. 68-71). 



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

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

 (Fig. 68, ec, en). 



3. There is usually what is known as a pulsating vacuole, 

 in which some of the more fluid cell-contents collect, to be 

 forced out of the vacuole again by the contraction of the denser 

 protoplasm (Fig. 68, pv). 



