100 PROTOZOOLOGY 



phosphate, which disappeared completely in 1-2 days when the 

 organisms were starved, and reappeared when food was given. 

 Schewiakoff did not see the extrusion of these crystals, but con- 

 sidered that these crystals were first dissolved and excreted by 

 the contractile vacuoles, as they were seen collected around the 

 vacuoles. In Amoeba proteus, Schubotz (1905) noted that the crys- 

 tals were of similar chemical composition and of usually bipyram- 

 idal or rhombic form, and that they measure about 2-5^ in 

 length and doubly refractile. Schaeffer (1920) observed calcium 

 phosphate crystals in three species of Amoeba and was inclined 

 to think that the form and dimensions of these crystals were 



Fig. 39. Examples of crystals present in Protozoa, a-e, in Parame- 

 cium caudatum (Schewiakoff), (a-d, XlOOO, e, X2600); f, in Amoeba 

 proteus; g, in A. discoides; h, in A. dubia (Schaeffer). 



characteristic of each species. Thus in Amoeba proteus, they are 

 truncate bipyramids, rarely flat plates, up to 4.5/i long; in A. dis- 

 coides, abundant, truncate bipyramids, up to 2.5At long; and in A. 

 dubia, variously shaped (4 kinds) few, but large, up to IOjjl, 12/x, 

 30m long (Fig. 39). 



Rowland detected uric acid in Paramecium caudatum and 

 Amoeba verrucosa. Luce and Pohl (1935) noticed that at certain 

 times amoebae in culture are clear and contain relatively a few 

 crystals but, as the culture grows older and the water becomes 

 more neutral, the crystals become abundant and the organisms 

 become opaque to transmitted light. These crystals are tubular 

 and six-sided, and vary in length from 0.5 to 3.5)U. They consid- 

 ered the crystals were composed of calcium chlorphosphate. Mast 

 and Doyle (1935), on the other hand, noted in Amoeba proteus 

 two kinds of crystals, plate-like and bipyramidal, which vary in 

 size up to Ifj, in length and which are suspended in alkaline fluid 

 to viscous vacuoles. These two authors believe that the plate-like 



