144 CYTOPLASMIC INCLUSIONS 



eludes a heterogeneous group of structures, including scattered endo- 

 plasmic granules and granules associated with contractile vacuoles or 

 fused to form heavy and permanent vacuolar membranes. A summary 

 of the known functions of these granules includes the excretion of ma- 

 terials through the contractile vacuoles, the formation of granules of 

 neutral fat, the storage of lipoids other than neutral fat, a secretory cycle 

 which does not involve lipoids, as well as many functions as yet unknown. 

 These functions are different, but in a broad sense they are all varieties of 

 secretion and in this respect conform to the Nassonov-Bowen theory of 

 the relationship between Golgi bodies and secretion. The restriction of 

 criteria for Golgi bodies to that of impregnation alone thus does not do 

 violence to the concept of Golgi bodies as originally developed in verte- 

 brate tissues. 



The Golgi bodies are simply those secretory bodies (exclusive of 

 mitochondria and segregation granules) which synthesize or store ma- 

 terials which can be preserved by Golgi-type fixatives, and after this 

 treatment are able to reduce (or adsorb the reduced metal) OSO4 or 

 silver nitrate. This is not a natural grouping, since on the one hand it 

 includes several specific types of secretion, and on the other hand it does 

 not include all types. In several cases the Golgi bodies can be classified 

 according to function or composition, and in this discussion they are 

 referred to as excretory granules, intermediate lipoid bodies (see p. 

 151), and, when the bodies are secretory in nature but the type of 

 secretion body unknown, secretory Golgi bodies. This leaves a miscel- 

 laneous group of Golgi bodies which are known only by their ability 

 to reduce osmium or silver and for which there is no evidence as to 

 either composition or function. Since the impregnation reactions them- 

 selves do not reveal homologies which must be based on composition 

 and function, the retention of the term Golgi body is merely a con- 

 venience to bridge the change from reliance on the nonspecific osmic 

 techniques alone to reliance upon specific cytochemical and physiological 

 criteria. 



Excretory Granules 



Ramon y Cajal (1903-4) was the first to suggest that the contractile 

 vacuole is equivalent to the Golgi reticulum of the cells of the Metazoa. 

 The first confirmation of this view was the demonstration in several 

 ciliates by Nassonov (1924) that this vacuolar region is osmiophilic. 



