104 PROTOZOOLOGY 



studied the pulsation of the contractile vacuoles of Paramecium 

 caudatum in fresh water as well as various salt concentrations, and 

 obtained the following measurements: 



Per cent NaCl in water 0.25 0.5 0.75 1.00 



Contraction period in second 6.2 9.3 18.4 24.8 163.0 

 Excretion per hour in body 



volumes 4.8 2.82 1.38 1.08 0.16 



The contractile vacuole also serves to remove from the body part 

 of soluble catabolic wastes, judged by numerous observations. 

 Weatherby (1929) showed that the excretory vacuole of Spiros- 

 tomum contains urea, and that of Didinium contains ammonia and 

 occasionally trace of uric acid. The number of the contractile vacu- 

 oles present in a given species as in various species of Paramecium, 

 is not always constant. Nor is its size constant. According to Taylor 

 (1920) the average size of the contractile vacuole of Euplotes patella 

 is 29/x at maximum diastole, but may become 45-50m in diameter 

 upon disturbance or after incision. The rate of pulsation is subject 

 to change with temperature, physiological state of the organism, 

 amount of food substances present in the water, etc. For example, 

 Rossbach observed in the three ciliates mentioned below the 

 pulsation of the contractile vacuole increased first rapidly and then 

 more slowly with the rise of the temperature of the water: 



Time in seconds between two systoles at 

 different temperature (C.) 



5° 10° 15° 20° 25° 30° 



Euplotes char on 61 48 31 28 22 23 



Stylonychia pustulata 18 14 10-11 6-8 5-6 4 



Chilodonella cuculluhis 9 7 5 4 4 — 



In Amoeba mira, Hopkins (1938) found that small vacuoles 

 (acid reaction) appear and coalesce with one another and also 

 with bacteria taken in as food, thus giving rise to larger ones 

 (alkaline reaction). These larger vacuoles after giving off substances 

 to the protoplasm by diffusion, are discharged. Thus the vacuole 

 system in this amoeba appears to perform not only digestive func- 

 tion, but also excretory function as excess water, food residues and a 

 substance stainable by janus green B, are extruded by way of this 

 system. 



Aside from the soluble forms, there often occur in the protozoan 

 body insoluble catabolic products in the forms of crystals and gran- 

 ules of various kinds. Schewiakoff (1893) first noticed that Para- 

 mecium often contained crystals (Fig. 41) composed of calcium phos- 

 phate, which disappeared completely in 1-2 days when the organ- 



