PLATE 1 



EXPLANATION OF FIGURES 



9 Typical foraging Spathidium. 



10 A common form when food is scarce. 



11 Optical section of total mount, stained with Delafield's haematoxylin, 

 to show macronuclear and micronuclcar apparatus. Seven micronuclei are pres- 

 ent, one at the posterior end above the contractile vacuole. 



12 Section (4;u) to illustrate the anterior paling of trichites and the trichites 

 distributed through the endoplasm; nuclear apparatus, etc., omitted. Heiden- 

 hain's iron haematoxjdin. 



13 Form of Spathidium in an early stage preparatory to encystment. 



14 Form shortly before encystment. 



15 Spathidium dividing. 



16 Division nearly completed. 



17 to 19 Spathidium swallowing a Colpidium. Successive stages. 



20 Form shortly after division or when quieting down preparatory to 

 encystment. 



Drawn by Miss J. E. Lovett. 



204 



