FIG. 1. Amoeba polypodia in the successive stages of division. The light spot is the contractile 

 vacuole, the dark the nucleus (after F. E. Schulze). 



FIG. 2. A, Quadrula symmetrica, after F. E. Schulze. B, Hyalosphenia lata, after F. E. 

 Schulze. C, Arcella vulgaris, after Hertwig and Lesser. D, Difflugia pyriformis (after Wal- 

 lich) completed. 



