General Morphology of the Protozoa 9 



layer, and Blepharisma undulans is said to shed its pellicle after treat- 

 ment with strychnine. The cilia are withdrawn and the body retracted, 

 leaving a space beneath the pellicle, and the ciliate later emerges through 

 the old cytostomal area or the region of the posterior contractile vacuole 

 (169). 



Surface layers of flagellates range from a delicate periplast or pellicle, 

 similar to that of certain amoebae, to thick tests or shells. The flexible 



Ir 







Fig. 1. 5. A, B. Ventral and dorsal thecal plates in Gonyaulax acatenella; 

 x560 (after Whedon and Kofoid). C. Vaginicola longicoUis, optical section of 

 lorica; xl40 (after Penard). D. Stokesiella lepteca, stalked lorica; xl060 (after 

 Stokes). E. Test of Euglypha alveolata; x350 (after Leidy). F. Difflugia corona; 

 xl35 (after Leidy). G. Tintinnopsis nucula, optical section of lorica; diagram- 

 matic; x570 (after Campbell). 



periplast of many Euglenida permits a characteristic euglenoid movement 

 ("metaboly"), but tends to maintain a characteristic form in the swim- 

 ming flagellate. This periplast presumably is a secreted layer, since it 

 becomes separated from the underlying cytoplasm in plasmolysis (22). 

 Thickened pellicular layers, as seen in LepocincUs and Phacus, may be so 

 firm that the body shows little change in shape. Such membranes are 

 often decorated with ridges, papillae or other markings. 



The theca of many Phytomonadida and Dinoflagellida is a secreted 



