104 ZOOLOGY SECi. n 



ment of the Protozoan series, since they show a degree of 

 differentiation attained nowhere else by a single cell. 



The Mycetozoa appear to have been derived from the common 

 amceboid-flagellate stock, since they are all predominantly amcs- 

 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 

 these relationships in a graphic form. 



