CYTOPLASMIC INCLUSIONS 151 



feeding stages and are used during hunger or encystment. Zinger ( 1933) 

 included all sudanophil particles as lipoid reserves, but digestive gran- 

 ules, mitochondria, as well as other bodies respond to Sudan III because 

 of their lipoid content. Zinger pointed this out, for in his conclusion he 

 states that the sudanophil bodies are more than reserve materials. How- 

 ever, until more is known of the functions of the intracellular lipoids, 

 it is impossible to indicate accurately the boundary between reserve lipoids 

 and those active directly in the metabolism of the cell. 



Lipoid reserves have been found in a large number of Protozoa (for 

 a detailed list see von Brand, 1935). Usually, if not always, these gran- 

 ules are in the endoplasm, either distributed at random, as in Ich- 

 thyophthhius (MacLennan, 1936), or concentrated at one end, as in 

 Anoplophrya (Eksemplarskaja, 1931). Although these visible lipoid 

 granules occur in many Protozoa, they are not universal. Trypanosoma 

 evansi lacks all lipoid reserves, a fact which is correlated with a lack of 

 lipase (Krijgsman, 1936). The Ophryoscolecidae and Cycloposthiidae, 

 noted for their tremendous glycogen reserves, have no important lipoid 

 reserves. Mesnilella multispkulata has no lipoid reserves, although five 

 other species of the same genus have many fat globules (Cheissin, 1930) . 



The formation of droplets of neutral fat inside a granule of fatty 

 acid has been demonstrated in 0/?<^//Vzi^ (Kedrowsky, 1931) and Ich- 

 thyophthirius (MacLennan, 1936) by the Nile blue sulphate method 

 (Fig. 41). Since, after staining with Nile blue sulphate, very small 

 quantities of fatty acid dissolved in neutral fat result in an intense blue 

 color rather than the pink which is characteristic of pure neutral fats, 

 the pink stain observed in the cases above indicates that there are no free 

 fatty acids in the neutral fat granules, as would be expected if the fats 

 were synthesized on the surface of these granules. The fatty acids and 

 glycerine dissolved in the endoplasm are first segregated into granules, 

 and in these granules the neutral fat is synthesized. Then this fat is segre- 

 gated into the visible droplets of pure neutral fat inside the active gran- 

 ules. These latter granules are typical Golgi bodies (MacLennan, 1936, 

 1940), as indicated by the name endoplasmic Golgi bodies. However, 

 since these are functionally an intermediate stage in the development of 

 the fat reserves, the descriptive term "intermediate lipoid body" is more 

 appropriate in a functional classification. 



In A. proteus the fat droplets grow in the cytoplasm without any in- 



