178 CYTOPLASMIC INCLUSIONS 



those bodies which are mitochondria, or which segregate neutral red 

 vitally. The term as used here is thus merely a convenient way to indicate 

 briefly certain techniques. Included in this group of granules are the 

 fatty acid bodies, which are simply a stage in the formation of neutral 

 fat granules and which have been called intermediate lipoid bodies. The 

 granules or membranes which are associated with the contractile vacuoles 

 are a separate group in composition and function, and are called excre- 

 tory granules. There is a third group which display a characteristic secre- 

 tory cycle but which are neither lipoidal in composition nor excretory 

 in nature (Ellis, 1937). For these bodies and other unknown granules, 

 the term Golgi body is appropriate, since it merely designates them ac- 

 cording to the techniques used and implies nothing as to their composi- 

 tion or functions. 



The term neutral red granule refers to any body which segregates 

 neutral red or similar basic dyes in the living normal protozoon. Again, 

 it is a term which indicates only the technique used and is a convenience 

 when there is no evidence as to function. In this group are the segrega- 

 tion granules, which accumulate and perhaps synthesize proteins and 

 similar materials, as in Opalina. The refractive bodies of Amoeba may 

 be included here because of the neutral red reaction and because of the 

 protein stroma, or they could be listed in the lipoid reserves because of 

 their high lipoid content. The digestive granules are a separate group 

 and are associated with the gastriole. One of the problems in this con- 

 nection is how these digestive granules differ in function and composi- 

 tion from the mitochondria, which may also be associated with digestion. 



Many different types of granules, some of them with the power to 

 segregate neutral red, are expelled from the cell in the formation of 

 shells, cysts, cement, and so forth, and are named secretion granules. 

 These granules should be given more attention, since they indicate a 

 situation similar to the secretion granules of gland cells. 



The reserve bodies have been separated on the basis of the material 

 stored — protein, lipoid, and carbohydrate — which also allows for the 

 various combinations which do occur, and which will permit further 

 subdivision when justified by an increase in the precision of cytochemical 

 methods. This is convenient in summarizing the reserves, but for final 

 classification it is unsatisfactory, since it ignores the differences in origin — 

 whether they are independent bodies, as the segregation granules of 

 Opalina and the paraglycogen granules of Poly plastron, or whether they 



