102 



THE PROTOZOA 



As a matter of fact, the beginnings of the various branches of the 

 Protozoa rest in complete obscurity, and the relationships of the sub- 



Fig. 56. Nuclearia delicatula Cientc. 

 A. Heliozoan phase. B. Rhizopod phase. 



groups are almost equally uncertain. There are a few interesting 

 forms, however, which are generally given as intermediate stages 



