PHYLUM PROTOZOA 



95 



of 



ment of the Protozoan series, since they show a degree 

 differentiation attained nowhere else by a single cell. 



The Mycetozoa appear to have been derived from the common 

 amoeboid-flagellate stock, since they are all predominantly amoe- 

 boid in the adult condition, flagellate when young. The Sporozoa 

 probably had a similar origin, but the characters of this class have 

 evidently been profoundly modified in accordance with their 

 parasitic mode of life. 



The diagram on the previous page is an attempt to express 

 jhese relationships in a graphic form. 



