PLASMODROMATA AND SARCODINA 



guinis, are with difficulty separated from the Hcemospovidia, or 

 parasites which mostly live in blood cells. For many reasons some 

 of these two groups of parasites were united together into one 

 order of the flagellates by Har' mann, 



Morphology. — Protozoan parasites vary in size from the large 

 Sarcocystidce in muscle to most minute forms in the blood [Hcemo- 

 protozoa). In fact, it is possible that some forms may exist which 

 we have not yet recognized, because their minute size prevents their 

 being visible to the human eye, even when aided by the highest 

 powers of the microscope. 



The parasites themselves consist of protoplasm, which in some 

 instances shows a modification into ectoplasm and endoplasm, the 

 former being clear and hyaline and the latter dark and granular. 

 In the protoplasm are to be found — (i) one or more nuclei, 

 (2) chromidiosomes and chromidia, (3) metachromatic granules, 

 (4) volutine granules, (5) metaplastic granules, (6) centrosomes, 

 (7) archopiasm, (8) rhizoplast, (9) vacuoli. 



(1) The nucleus in its simplest form is merely a collection of 

 smaller or larger particles of chromatin (chromidiosomes or chro- 

 midia). A very simple form is that termed Protokary on, in which 

 one large chromidial mass (the Karyosome) lies in a delicate achro- 

 matic network of linin inside a vacuole filled with nuclear sap, 

 called enchylema. Some chromidia may or may not be situated 

 peripherally as well as more centrally. There is no definite mem- 

 brane. The next advance is the vesicular nucleus, which consists 

 of a definite nuclear membrane separating it from the cytoplasm. 

 Inside this membrane there is an achromatic framework made of 

 linin; a nuclear fluid or enchylema, lumps of a substance called 

 plastin giving rise to the nucleolus, so common in the Metozoa and 

 so rare in the Protozoa, and in association with chromatin to the 

 karyosome, which in this instance is called the endosome, or Binnen- 

 korper. The granular nucleus is a further evolution, and is pro- 

 duced by a more scattered condition of the chromatin. 



The nucleus is therefore a complex body composed of chromatic 

 and achromatic substances. It may be single, or divided into two 

 principal masses — trophonucleus or nutrition-nucleus and kineto- 

 nucleus or motion-nucleus, or into macronucleus and micronucleus. 

 The latter are quite different from the tropho- and kinetonuclei, for 

 the macronucleus is trophic and kinetic, while the micronucleus is 

 purely reproductive. The former is typically seen in the trypano- 

 somidse and the latter in the heterokaryota. 



(2) Chromidiosomes are the smallest particles of chromatin 

 which, when massed together, give rise to the chromidia which may 

 be intranuclear or extranuclear. (3) The metachromatic granules 

 or chromatoid grains represent stages in the anabolism or katabolism 

 of chromatin. (4) Volutine granules stain like chromatin. They 

 are composed of nucleic acid in combination, and represent reserve 

 food material for the nucleus. (5) Metaplastic granules are products 

 of cytoplastic anabolism or katabolism. (6) Centrosome is a 



