MORPHOLOGY 45 



to Reichenow, Jollos observed that in Arcella the nuclei persisted, 

 but were thickly covered by chromidial-net which could be cleared 

 away by artificial digestion to reveal the two nuclei. In Diffiugia, the 

 chromidial-net is vacuolated or alveolated in the fall and in each 

 alveolus appear glycogen granules which seem to serve as reserve 

 food material for the reproduction that takes place during that 

 season (Zuelzer), and the chromidia occurring in Actinosphaerium 

 appear to be of a combination of a carbohydrate and a protein 

 (Rumjantzew and Wermel, 1925). Apparently the widely distributed 

 volutin (p. 114), and many inclusions or cytozoic parasites, such as 

 Sphaerita (p. 893), which occur occasionally in different Sarcodina, 

 have in some cases been called chromidia. By using Feulgen's nucleal 

 reaction, Reichenow (1928) obtained a diffused violet-stained zone 

 in Chlamydomonas and held them to be dissolved volutin. Calkins 

 (1933) found the chromidia of Arcella vulgaris negative to the nucleal 

 reaction, but by omitting acid-hydrolysis and treating with fuchsin- 

 sulphurous acid for 8-14 hours, the chromidia and the secondary 

 nuclei were found to show a typical positive reaction and believed 

 that the chromidia were chromatin. Thus at present the real nature 

 of chromidia is still not clearly known, although many protozoolo- 

 gists are inclined to think that the substance is not chromatinic, but, 

 in some way, is connected with the metabolism of the protozoan. 



The cytoplasm 



The extranuclear part of the protozoan body is the cytoplasm. It 

 is composed of a colloidal system, which may be homogeneous, granu- 

 lated, vacuolated, reticulated, or fibrillar in optical texture, and is 

 almost always colorless. The chromatophore-bearing Protozoa are 

 variously colored, and those with symbiotic algae or cryptomonads 

 are also greenish or brownish in color. Furthermore, pigment or 

 crystals which are produced in the body may give protozoans vari- 

 ous colorations. In several forms pigments are diffused throughout 

 the cytoplasm. For example, many dinoflagellates are beautifully 

 colored, which, according to Kofoid and Swezy, is due to a thorough 

 diffusion of pigment in the cytoplasm. 



Stentor coeruleus is beautifully blue-colored. This coloration is due 

 to the presence of pigment stentorin (Lankester, 1873) which occurs 

 as granules in the ectoplasm (Fig. 14). The pigment is highly re- 

 sistant to various solvents such as acids and alkalis, and the sun- 

 light does not affect its nature. It is destroyed by bleaching with 

 chlorine gas or with potassium permanganate, followed by immer- 

 sion in 5 per cent oxalic acid (Weisz, 1948). Several species of Blepha- 



