CYTOLOGY 331 



is formed between them, while the karyosome breaks up into chromo- 

 somes, which arrange themselves upon the spindle as an equatorial plate. 

 In this case the blepharoplast is undoubtedly functioning as a true centro- 

 some. In many respects the division of the nucleus of Cercomonas longi- 

 cauda, as also that of Heteromita uncinata, resembles that of the kinetoplast 

 of Herpetomonas muscarum, in which, however, the parabasal does not 

 form chromosomes, but merely splits into two equal parts (Figs. 68 and 259). 

 Kobertson (1913) has shown that in Trypanosoma gambiense division of 

 the kinetoplast may take place in such a manner that the two daughter 

 blepharoplasts are connected by a fibre, at the central point of which the 

 parabasal is situated. When the daughter blepharoplasts still further sepa- 

 rate, the parabasal divides and two kinetoplasts are thus formed. Such 

 a method of division has a striking resemblance to that frequently seen 



A 1 /\ /\ An 



Fig. 158. — Dividing Kinetoplasts of Rerpetomonas muscarum. (After Wenyon, 



1913.) 



Upper row after fixation in Hermann's fluid. 

 Lower row after fixation in Schaiidinn's fluid. 



in division of the nucleus itself. This raises the question of the nuclear 

 nature of the kinetoplast. Hartmann (1907), assuming this to be the 

 case, regards the flagellates of this group as possessing two nuclei, and 

 places them in a special order, the Binucleata. The evidence of the true 

 nuclear nature of the kinetoplast in the sense that it is a second nucleus 

 is, however, wanting. The mitotic divisions of the kinetoplast with 

 formation of chromosomes, wdiich some observers have recorded, can 

 hardly be taken seriously. 



If, however, such a mitotic division actually occurred, it would be 

 strong presumptive evidence of the nuclear nature of the kinetoplast. 

 From analogy with other flagellates, the terminology here employed 

 appears to be the safest one. In many flagellates, axonemes arise from a 

 blepharoplast in close association with which is a parabasal body which 



