164 



CYTOPLASMIC INCLUSIONS 



appear as minute bodies at the lower limits of visibility, embedded in 

 the chromatin net during the feeding stages of the ciliate but not during 

 encystment. The macronucleus is positive to Feulgen's reagent without 

 preliminary hydrolysis during the formation of these granules, but at 

 no other time. It seems probable that food materials are built up in the 

 macronucleus into chromatin, which is then split into a group contain- 

 ing iron and nucleic acid and another protein group which lacks these 

 substances. The first group is used to rebuild more chromatin and the 

 latter group is segregated into the granules which are ejected into the 



Figure 66. The forma- 

 tion and release of protein 

 granules from the macro- 

 nucleus of Ichthyophthi- 

 ritis mullifiliis, Feulgen- 

 light green. (After Mac- 

 Lennan. 1936.) 



cytoplasm. Since granules of this type are found in both the macro- 

 nucleus and the cytoplasm of so many ciliates, this is probably quite a 

 general phenomenon. The Protociliata lack macronuclei, but perform 

 this same function by the segregation apparatus. 



The balls of chromatin and other macronuclear fragments which are 

 extruded during the various types of macronuclear reorganization are 

 only incidentally reserve material, if at all, and will be considered in 

 detail in the chapters on nuclear phenomena. 



The crystals which are common in various Protozoa are often con- 

 sidered to be excretory products, and in some cases have been identified 

 as uric acid (for a discussion of this work, see Reichenow, 1929) . Recent 

 work (Mast and Doyle, 1935b) shows, however, that some of the crystals 

 must be regarded as reserve material. A. proteus contains two types of 

 crystals, a bipyramidal type and a plate-like type, which are suspended 

 in vacuoles containing an alkaline fluid. A careful study of spectroscopic 



