160 CYTOPLASMIC INCLUSIONS 



Protein Reserves 

 This term is one of convenience and, as in the case of the term Hpoid, 

 cannot be taken in a strict sense, but is used here to include, besides 

 true proteins, bodies which contain hpoids or carbohydrates, as well as 

 proteins, amino acids, nucleic acid, and so forth. Since most of the fixing 

 agents precipitate at least the protein portions of such granules, many 

 have been described, although relatively few have been identified by 

 acceptable microchemical methods. For this reason they have been de- 

 scribed under a variety of names, many of which mention incidental 

 staining properties. Some of the names which are most securely em- 

 bedded in the literature are chromidia, volutin, metachromatic granules, 

 basophilic granules, chromatoidal bodies, and albuminoid reserves. The 

 confusion in these terms is best illustrated by chromidia. This was orig- 

 inally used to designate chromatin bodies which are extruded into the 

 cytoplasm from the nucleus (Hertwig, 1902) and which have the abil- 

 ity to reaggregate to form new nuclei. Although this interpretation has 

 been disproved, the name may be retained to designate these granules 

 (Meyers, 1935). In other cases it is used to designate nonchromatin ma- 

 terial which is supposed to be extruded from the nucleus (Dapiels, 

 1938). Other authors use it even more loosely to designate basophilic 

 and metachromatic cytoplasmic bodies which are secretory in nature 

 (Campbell, 1926). The elimination of the original meaning was due to 

 the improvement of both cytoplasmic and nuclear methods, accompanied 

 by detailed studies of life cycles. The last stronghold of this theory — 

 the Foraminifera — was eliminated by the tracing of the nuclear history 

 in live Patellina throughout the vegetative and sexual stages, with a 

 complete demonstration of the cycle with moving pictures (Meyers, 

 1935). The exclusion of chromidia in the original sense, with respect 

 to the cells of the Metazoa, has already been accepted (Wilson, 1928). 

 Many chromidia are actually mitochondria ( Faure-Fremiet, 1910) 

 which contain a high percentage of protein and are therefore resistant 

 to routine fixatives. This probably led to one revival of the chromidial 

 theory, according to which all cytoplasmic structures are formed from 

 mitochondria, which in turn originate from the nucleus as chromidia. 



Alexeieff in a series of works on the Flagellata strives to prove that all cell 

 structures are formed at the expense of mitochondria. The latter, according to 

 Alexeieff, in their turn are not autonomic, as the majority of investigators 



