BINUCLEATA 217 



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 characteris- 

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

 ing been modified as the result of cell parasitism, do not do so. This grouping to- 

 gether of the blood flagellates and sporozoa under the name Binucleata has been con- 

 sidered 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 bacteria would be the lower types and the fungi and protozoal organ- 

 isms 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 endo- 

 plasm or endosarc. The functions of the ectosarc are protective, locomotor, ex- 

 cretory 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* chro- 

 matin may stain even more intensely. When chromatin is scattered through the 

 cytoplasm, as extranuclear aggregations, such chromatin granules are called chro- 

 midia. 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 achro- 

 matic reticulum is contained the nuclear sap or karyolymph. As a rule an achro- 

 matic nuclear membrane, continuous with the reticulum, separates the nucleus 

 from the cytoplasm. In addition we have a substance which is achromatic (plas- 

 tin) and which is the imbedding substance for chromatin grains. These plastin 

 chromatin combinations are called karyosomes. The nucleoli are probably pure 

 plastin. Plastin is to be regarded as a secretion or modification of chromatin 



