436 THE CONTRACTILE VACUOLE 



vestigated other more or less spherical cytoplasmic inclusions, which 

 they call "cytoplasmic refractive bodies." The outer layers of these 

 bodies are readily stained by neutral red and osmium, whereas the central 

 portions react negatively to osmium and stain but faintly with neutral 

 red. Apparently these are the same structures studied by Brown, who 

 believes them to give rise to minute vacuoles which are precursors to 

 contractile vacuoles. The beta granules are not blackened by osmium. 

 Many of these granules are usually situated close to the contractile 

 vacuole, while others are scattered throughout the entire cytoplasm. The 

 pulsation frequency of the vacuole is proportional to the number of 

 beta granules remaining after some have been removed by operation, 

 indicating a close relationship between granules and vacuole function. 

 Removal of most of these granules results in the death of the organism. 

 The relationship between the contractile vacuole and cytoplasmic in- 

 clusions in Amoeba is puzzling. One would be inclined to accept, at 

 least tentatively, the idea of the origin of vacuoles in the beta granules 

 which surround it, were it not for the fact that in a variety of other 

 Protozoa the vacuole has been seen to originate as minute droplets in the 

 region of the cell occupied by osmiophilic granules. Yet in A. proteus 

 the granules among which the vacuole apparently arises are not osmio- 

 philic nor stainable by neutral red, but are stainable by Janus green. It 

 might be suggested that the situation in Amoeba is the reverse to what 

 it appears to be in other Protozoa, but such a suggestion offers no satis- 

 faction. A more likely explanation lies in the uncertainty of identification 

 of these cytoplasmic inclusions. Some authors (e.g.. Hall, 1930a) consider 

 the vacuome, which is neutral-red stainable, identical with the Golgi 

 apparatus, which is osmiophilic; this Hall observed to be true in Trich- 

 amoeba. Others (e.g., MacLennan, 1933) have identified both neutral- 

 red stainable and osmiophilic granules as separate structures within the 

 same organism. Apparently Dunihue (1931) finds the same in 'Para- 

 mecium. Further, MacLennan observed that the only granules in Eudi- 

 plodinium which can be impregnated with osmium are those found in 

 the vacuolar region; yet in a study of living material, it was shown that 

 this region is composed of granules which originate in the surrounding 

 ectoplasm. Therefore, these granules, as they assemble in the vacuolar 

 region, undergo some change, either chemical or physical or both, which 

 makes them osmiophilic. It has been suggested at one time or another 



