250 THE PROTOZOA 



NOTE. Hartmann and others have grouped the Haemosporozoa and the Haemo- 

 flagellata in an order BINUCLEATA. The main characteristic is the possession of 

 two differentiated nuclei, the kinetonucleus and the trophonucleus, at some develop- 

 mental or transitional stage. While trypanosomes plainly show these characteristics 

 certain others, as the malarial parasites and the leishman-donovan bodies, having 

 been modified as the result of cell parasitism, do not do so. This grouping together 

 of the blood flagellates and sporozoa under the name Binucleata has been considered 

 by many protozoologists as possibly convenient but not resting on sufficient ground 

 to cause organisms with similar life histories as Plasmodium and Coccidium to be 

 separated and the former to be placed with the blood flagellates in a new grouping. 



THE PROTOZOA 



By the term protozoa we understand a branch of animals in which a 

 single cell is morphologically and functionally complete; it is not one of 

 a number of cells going to make up a complex individual and dependent 

 on such a combination as is the case with the metazoa (there is no 

 differentiation into tissues in protozoa). 



Recognizing the fact that certain protozoa have characteristics which make 

 it impossible to draw a distinction between them and plants Haeckel has proposed the 

 name Protista as a designation for all simple and primitive living organisms whether 

 they be plants or animals. In such a classification we would have the kingdom of 

 Protista as well as the animal and vegetable kingdoms. In such a grouping the bac- 

 teria would be the lower types and the fungi and protozoal organisms the higher ones. 



The protozoal cells are made up of protoplasm which is divided into nucleus and 

 cytoplasm. The cytoplasm is at times separated into an external, hyaline portion, 

 the ectoplasm or ectosarc and an internal granular portion, the endoplasm or endo- 

 sarc. The functions of the ectosarc are protective, locomotor, excretory and sensory; 

 those of the endosarc trophic and reproductive. Protozoa may be holozoic (animal 

 like) or holophytic (plant like), saprophytic (fungus like), or parasitic (living at the 

 expense of some other animal or plant). 



The nucleus is characterized by concentration of the so-called chromatin sub- 

 stance of the cell. This chromatin however is usually combined with achromatin. 

 The usually accepted test for chromatin is the staining affinity for basic aniline dyes. 

 This test is now known to be unsatisfactory as other substances than chromatin may 

 stain even more intensely. When chromatin is scattered through the cytoplasm, as 

 extranuclear aggregations, such chromatin granules are called chromidia. There are 

 cells where the chromidia take the place of the nucleus and from which a nucleus 

 may be formed. Chromidia may arise from nuclei and nuclei from chromidia. The 

 nucleus is made up of a network of linin in which achromatic reticulum is contained 

 the nuclear sap or karyolymph. As a rule an achromatic nuclear membrane, con- 

 tinuous with the reticulum, separates the nucleus from the cytoplasm. In addition 

 we have a substance which is achromatic (plastin) and which is the imbedding sub- 

 stance for chromatin grains. These plastin chromatin combinations are called 

 karyosomes. The nucleoli are probably pure plastin. Plastin is to be regarded as a 





