PHYSIOLOGY 



105 



isms were starved, and reappeared when food was given. Schewiakoff 

 did not see the extrusion of these crystals, but considered 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 crystals were of similar chemical 

 composition and of usually bipyramidal or rhombic form, and that 

 they measured about 2-5^ in length and doubly refractile. Schaeffer 

 (1920) observed calcium phosphate cr3^stals in three species of 



B □ 



Fig. 41. Examples of crystals present in Protozoa, a-e, in Paramecium 

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

 g, in A. discoides; h-1, in A. duhia (Schaeffer). 



Amoeba and was inclined to think that the forms and dimensions of 

 these crystals were characteristic of each species. Thus in Amoeba 

 proteus, they are truncate bipyramids, rarely fiat plates, up to 4.5jLt 

 long; in A. discoides, abundant, truncate bipyramids, up to 2.5^ 

 long; and in A. dubia, variously shaped (4 kinds), few, but large, up 

 to 10m, 12/x, 30m long (Fig. 41). 



Rowland detected uric acid in Paramecium caudatum and Amoeba 

 verrucosa. Luce and Pohl (1935) noticed that at certain times amoe- 

 bae 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 in 

 transmitted light. These crystals are tubular and six-sided, and vary 

 in length from 0.5 to 3.5m. They considered the crystals were com- 

 posed of calcium chlorophosphate. 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 7m in length and 

 which are suspended in alkaline fluid to viscous vacuoles. These two 

 authors believed that the plate-like crystals are probably leucine, 

 while the bipyramidal crystals consist of a magnesium salt of a sub- 

 stituted glycine. Other crystals are said to be composed of urate, 

 carbonate, oxalate, etc. 



Another catabolic product is the haemozoin (melanin) grains 



