280 



BIOLOGY OF THE PROTOZOA 



istic. Reproduction occurs hy division within the shell the valves 

 being pushed apart by swelling of the gelatinous contents when the 

 daughter cells are mature. Fertilization by anisogamy. 



Family 3. Polytomidae, Poche.— These are colorless saprozoic 

 forms ellipsoidal in shape {Polytoma) or with a truncated anterior 



Fig. 134. — Sphardia lacustris. (After Hazen.) 



end recalling the Cryptomonadida (Parapolytovia). Starch is 

 formed and collected at the posterior end of Pdytoma but is absent 

 in Par a polytoma. Reproduction by division into two or four 

 daughter cells, the second division in the latter case being transverse. 

 Blepharoplasts and flagella are lost and reformed at each division 

 (Jameson). 



