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HANDBOOK OF PROTOZOOLOGY 



plasm. The ectoplasm appears on the periphery as a hyaline and 

 homogeneous zone. The endoplasm is greater in volume and 

 more fluid and may be granulated or alveolated. These two 

 parts, however, are not distinctly separated parts of the cyto- 

 plasm. They are freely interchangeable with each other. A 

 protozoan may show a conspicuous ectoplasmic zone at one 

 time, and may not show it at all at other times. This is true as a 

 rule in Sarcodina. In pellicle-possessing Protozoa, as in the 

 Ciliata, the ectoplasm and the endoplasm appear to be per- 

 manently differentiated during the trophic life of the individual. 

 The majority of Protozoa possess a definite membrane which 

 surrounds the body. This is commonly called the pellicle, or 

 periplast, and fits the body surface more or less closely. The 



Fig. 6 a. Paramecium caudatum treated with alcohol, showing somewhat 



distended pellicle with its pores for cilia. X about 150. 



b-e. Changes in body-form of Euglena viridis. X about 350. 



presence of a pellicle is easily demonstrated by treating a ciliate 

 with a dehydrating reagent. The protoplasm shrinks and 

 pulls away from the pellicle, and the latter becomes somewhat 

 distended by the accumulation of a watery fluid and to a 

 certain extent by the pressure of the cover glass (Fig. 6). In life 

 the pellicle is elastic and expansible to a considerable extent, as 

 will be noted by examining Euglena viridis (Fig. 6). In some 

 forms, the pellicle is marked by striation as in Phacus .(Fig- 40), 

 by ridges, by furrows, or by nodules arranged in definite rows, 

 as in Euglena spirogyra (Fig. 40). In others, again, the pellicle 



