CYTOPLASMIC INCLUSIONS 171 



bodies (excretory Golgi) around the contractile vacuoles of Ichthy- 

 ophthmus. 



These comparisons demonstrate that with respect to actual composition 

 not even one single type of granule is found throughout these five species 

 of Protozoa, and the apparent universal presence of certain types of 

 granules is due to the lack of specificity in Janus green, neutral red, 

 osmic acid, and other stains. This is demonstrated in spite of the fact 

 that the known composition of these bodies can be stated only in 

 qualitative terms which are actually very broad — i.e., lipoid, non-lipoid, 

 protein, and so forth. 



A comparison on the basis of composition alone is open to criticism 

 if it is not checked from other angles. The segregation apparatus of 

 Opalina may be aqueous vacuoles, dense protein bodies, or it may contain 

 bile pigments, depending on the medium and the temperature. Using 

 composition alone as a criterion (or the neutral red reaction, for that 

 matter), these granules would be separately classified, actually Ke- 

 drowsky showed they are the same granules with the same function — 

 segregation and synthesis. In this case the stain reactions and the compo- 

 sition are incidental, and they are important in the classification of the 

 segregation apparatus only if they can be used to reveal the function. 

 Can groups of granules be demonstrated if the granules are compared, 

 not on the basis of structure nor of composition, but on function? If so, 

 are any of these groups represented in all of these five species which 

 we are considering? This comparison cannot be in any way as complete as 

 the comparison based on staining reactions and composition, since for 

 the most part this knowledge is restricted to those functions which have 

 a definite morphological expression — digestion, storage, external secre- 

 tion, and so forth. The apparent emphasis on these functions should not 

 be considered as an implication that these are the only functions in which 

 the cytoplasmic granules may play a role, but as an inverse expression 

 of the difficulties of localizing functions which do not produce visible 

 structures. 



The segregation and storage of protein reserves is obvious morpho- 

 logically and the materials which are stored can be identified by adequate 

 cytochemical methods. All the five Protozoa, again with the exception 

 of Flabellula, have visible stores of proteins or derivative substances. 



