128 CYTOPLASMIC INCLUSIONS 



and external factors and that it cannot be considered specific in the 

 sense that it combines with a single definite substance. 



Since many factors are involved in the segregation of neutral red, 

 it is to be expected that more than one type of granule will be revealed 

 by the use of this and similar dyes. Conclusive evidence of this lack 

 of specificity is furnished by several Protozoa in which two or more 

 types of granules are able to segregate neutral red at the same time, i.e., 

 under identical conditions. Dangeard (1928) stained two types of 

 granules in Euglena with neutral red — the vacuome and the mucous ap- 

 paratus. The latter group may be extruded to form a mucous envelope 

 or mucous hairs — an interesting example of true external secretion, and 

 comparable to the staining of secretion granules in Metazoa by neutral 

 red. However, Dangeard rejected the mucous apparatus as vacuome 

 because it retains the neutral red after the death of the cell, while the 

 other granules — the true vacuome — do not. Finley (1934) found four 

 different groups of granules which segregate neutral red in Vorticella: 

 pellicular secretions, pellicular tubercles, thecoplasmic granules, and re- 

 fractile granules. He was careful to control the staining to avoid over- 

 staining, so that his results cannot be questioned on that ground. Bush 

 (1934) found in Haptophyra two sets of granules which are discon- 

 tinuous in size and distribution. Mast and Doyle (1935b) complete the 

 picture by showing that three groups of granules stain in Amoeba: 

 vacuole refractive bodies, refractive bodies, and blebs on crystals, and 

 they proved experimentally that these bodies are different in origin and 

 in fate. The experiments of Kedrowsky (1931) on Opalina show the 

 reverse picture — under certain feeding conditions, the growing segre- 

 gation vacuoles lose their ability to take up neutral red, just as they do 

 in vertebrate eggs. Hall and Loefer (1930) showed that the granules 

 in Euglypha may vary in the same specimen from pink to bluish red 

 or red violet. 



Since neutral red stains several different groups of granules and also 

 does not stain all stages of the same granule, it does not of itself reveal 

 fundamental homologies, and it seems to me to be unjustifiable to group 

 all of these bodies as vacuome or under any other catchall term. As a 

 preliminary step toward an accurate classification of this group, the 

 digestive granules — i.e., those neutral red bodies associated with the 

 gastrioles — are separated from the segregation granules which cor- 



