Figure 4. Diagrammatic representation of several large species of unicel- 

 lular organisms, all drawn to the same scale. Nuclei are stippled, vacuoles 

 are outlined. 1. Spirostomum ambiguum (posterior half only). 2. Actino- 

 sphaerium eichhorni (pseudopodia amputated). 3. Diffluglia corona. 4. Fron- 

 tonia leucas. 5. Colpoda cucullus. 6. Colpidium colpoda. 7. Arcella den- 

 tata. 8. Ameba proteus. 9. Spirogyra bellis. 10. Stylonychia pustulata (side 

 view). 11. Paramecium caudatum. 12. Actinophrys sol. Linear magnifica- 

 tion X175. 



