CYTOPLASMIC INCLUSIONS 157 



cytoplasmic granules, is performed in the one case by a nuclear structure 

 and in the other case by a neuromotor structure. 



The differentiation between the various carbohydrates found in the 

 Protozoa is based on their staining reactions and solubility, since the 

 exact nature of the sugars involved in the formation of protozoan poly- 

 saccharides is unknown. Zhinkin (1930) and von Brand (1935) pointed 

 out that this is unsatisfactory and contend that no separation should be 

 made from glycogen until this is known. However, the differences are so 

 pronounced that it is convenient to retain the name paraglycogen. 



Soluble glycogen as found in vertebrate liver cells is relatively rare. 

 The diffuse materials found in Paramecium and Bursaria are probably 

 of this type. The commonest carbohydrate is paraglycogen, distinguished 

 by Biitschli (1885) from glycogen on the basis of its relative insolubility 

 in water as compared with true glycogen. It is digested by ptyalin and 

 diastase and the sugar produced reduces Fehling's solution. It stains a 

 light brown in iodine and brown or brown purple in iodine-sulphuric 

 acid or chlor-zinc-iodide. Probably all of the granular reserves of carbo- 

 hydrate in Protozoa are paraglycogen or some similar relatively insoluble 

 compound. The reserve granules of the flagellates of termites have been 

 identified as glycogen (Yamasaki, 1937a; Kirby, 1932); but in the re- 

 lated flagellates of the wood roach, since the Protozoa contain no enzyme 

 capable of breaking down glycogen, it has been suggested that the gran- 

 ules which stain with iodine consist of some other product which results 

 from the breakdown of cellulose (Cleveland, 1934). The material in 

 the platelets of the Ophryoscolecidae has been named ophryoscolecin on 

 the ground that it is unique in this family and is more like cellulose than 

 paraglycogen (Dogiel and Fedorowa, 1925). It was later identified as a 

 hemicellulose (Strelkow, 1929). This interpretation is based on slight 

 variations in solubility and color reactions, but other authors, using some 

 of the same methods and some different methods, were not able to find 

 any difference between the reactions of paraglycogen and the platelets 

 (Schulze, 1922, 1924, 1927; Weineck, 1931, 1934; MacLennan, 1934). 

 However, such arguments cannot be settled, as von Brand suggests, until 

 the exact structure of these polysaccharides is known, and the term para- 

 glycogen in this discussion is used in a rather general sense for carbo- 

 hydrates more insoluble in water than glycogen and differing in color 

 reactions from starch and cellulose. 



