234 



THE PROTOZOA 



nuclear apparatus varies in different forms, even in the same species, 

 as will be seen in the description of the reproductive processes. 



The marine Foraminifera, so far as they have been investigated, 

 show a well-marked alternation of generations in their life-history, 



si. 



FIG. 95. Polystometta crispa : decalcified specimens to show the structure of the 

 two forms. A, The megalospheric type ; B, the microspheric type : b, the 

 central chambers of the latter more highly magnified ; r., retral processes ; 

 st, communications between the chambers. From Lister. 



combined with dimorphism in the adult condition. An example is 

 Polystomella, which has been investigated by Lister (285) and 



