38 PROTOZOOLOGY 



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). Apparently the widely distributed 

 volutin (p. 101), and many inclusions or cytozoic parasites, such as 

 Sphaerita, which occur occasionally in different Sarcodina, have in 

 some cases been called chromidia. Bj^ using Feulgen's nucleal reac- 

 tion, 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 cytosome 



The extranuclear part of the protozoan body is the cytosome. 

 It is composed of the cytoplasm, a colloidal system, which may be 

 homogenous, granulated, vacuolated, reticulated, or fibrillar in 

 optical texture, aud 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. Fur- 

 thermore, pigment or crystals which are produced in the body, may 

 give protozoans various colorations. In several forms pigments are 

 diffused throughout the cytoplasm. For example, many dinoflagel- 

 lates are beautifully colored, which, according to Kofoid and Swezy, 

 is due to a thorough diffusion of pigment in the cytoplasm. Stentor 

 coeruleus is ordinarily blue-colored, the pigment stentorin (Lankester) 

 is lodged as granules between the surface striae; and rose- or purple- 

 coloration of several species of Blepharisma appears to be due to a 

 special pigment, zoopurpurin (Arcichovskij) which is said to be 

 lodged in the ectoplasmic granules often called protrichocysts (p. 65). 

 The development of zoopurpurin is definitely correlated with the 

 sun-light, as shown by Giese. Deeply pink specimens will lose color 

 completely in a few hours when exposed to strong sun-light and the 

 recoloration takes place in darkness very slowly. 



The extent and nature of the cytosomic differentiation differ 

 greatly among various groups. In the majority of Protozoa, the 

 cytoplasm is differentiated into the ectoplasm and the endoplasm. 



