1916] Sivezy: Ki)ieto)iuclciis of FlogeHates 189 



systemen erfiillen. " He does not state whether, before reaching the 

 next stage of evolution, the nucleus is dropped out, leaving the pole- 

 plate as the centrosome or central spindle, or vice versa, or whether 

 both structures are transformed into one organelle. 



A second step is reached in Paramoeha eilhardi, in which the 

 " Nebenkorper " functions as a central spindle, as does also the "cen- 

 tralkorper" of the diatoms. A still further advance is found in the 

 trypanosomes with their tropho- and kinetonuclei. As a result of his 

 work on these forms Schaudinn came to the conclusion that a condition 

 of binuclearity was found in all cells, metazoan as well as protozoan. 



These theories of Schaudinn 's were further elaborated and ampli- 

 fied by his followers. Foremost among these investigators has been 

 Hartmann, whose work has resulted in a new system of classification 

 for some groups of the Protozoa. In connection with Prowazek 

 (1907), he expanded this theory to its utmost capacity, finding a sec- 

 ond nucleus in most forms of the Protozoa where, to the unaided 

 imagination, but one such structure is actually present. In such forms 

 as the Amoeba, for example, the central karyosome of the nucleus be- 

 comes the second nucleus. 



In his system of the Protozoa (1907) he creates a new order, the 

 Binucleata, for all those forms which have a second nuclear structure. 

 This order includes the Haemosporidia as well as the Haemoflagellata. 



No attempt has been made in the following discussion to deal with 

 the earlier questions that have been thus briefly touched upon here, 

 except in so far as they relate to the present binuclear theory of Hart- 

 mann. This theory has been a gradual outgrowth and transformation 

 of the earlier ones, many parts of which have been discarded in the 

 light of newer observations and facts. 



An attempt will be made, however, to estimate the present value 

 of this theory in its relation to the more recent investigations on these 

 flagellates, as well as to give different interpretation to some of the 

 earlier observations on which this theory was founded. 



C. THE ORDER BINUCLEATA 



The forms included by Hartmann in the order Binucleata cover a 

 wide range of protozoans, apparently differing in phylogenetic deri- 

 vation as well as in structure. The basic principle of his classification 

 is nuclear dimorphism as exhibited in the trypanosomes, which he also 

 claims to have established in the Haemosporidia as well. The accept- 



