BLEPHAROPLAST PARABASAL KINET0PLA8T 117 



AVhen a flagellate is about to divide, the blepharoplast is usually the 

 first structure to show any indication of division. It becomes elongated 

 and constricted into two parts. Very often the two daughter blepharo- 

 plasts (or two groups of daughter blepharoplasts when several are present) 

 remain connected by a fibre which may be called the paradesmose, as 

 suggested by Kofoid and Swezy (1915), to distinguish it from the centro- 

 desmose which unites the daughter karyosomes, or centrioles which are 

 supposed by some observers to occur within the karyosome, during division 

 (Fig. 272). As the blepharoplast elongates and divides and the daughter 

 blepharoplasts separate, the parabasal also becomes elongated and divides. 

 If several parabasals are present, without dividing individually, they 

 separate into two approximately equal groups. The blepharoplast thus 

 leads the way in division of the parabasal. It sometimes happens that 

 the blepharoplast divides before the parabasal shows any signs of division. 

 A figure may be produced in w^hicli the two daughter blepharoplasts are 

 connected by a paradesmose, at the centre of which the still undivided 

 parabasal lies. The parabasal now divides, and the two halves move 

 towards the daughter blepharoplasts. There is some resemblance to 

 mitosis in this type of division, which has been employed as an argument 

 in support of the view that the blepharoplasts are centrosomes and 

 that the kinetoplast is actually a nucleus. The parabasal, however, 

 does not form chromosomes, nor are spindle fibres developed between 

 the blepharoplasts, though some claim to have observed these structures 

 during the division of the kinetoplast of trypanosomes. After the 

 blepharoplast and parabasal have commenced to divide, the nucleus 

 itself begins to show signs of division. 



In flagellates like Heteromita uncinata and Cerco-monas longicavda, in 

 which the blepharoplast is on the nuclear membrane, a condition is 

 seen in which the blepharoplast appears to function as a centrosome 

 (Fig. 68). The blepharoplast upon the membrane divides, and the two 

 halves separate. They finally take up positions at opposite poles of the 

 nucleus, and a definite spindle is formed between them. The karyosome 

 breaks up, and chromosomes appear at the 'equator of the spindle. The 

 chromosome plate divides into two daughter plates which move towards 

 the blepharoplasts. Finally, the nuclear membrane is divided, the 

 chromosomes disappear, and with the formation of the karyosomes the 

 nuclei are reconstructed. 



It seems difficult to resist the conviction that in such a division the 

 blepharoplast has fulfilled the function of a centrosome. Its behaviour, 

 however, may be merely due to its position on the nuclear membrane, 

 for in flagellates like Parajpolytoma satura, described by Jameson (1914), 

 in which the blepharoplast is separated from the nuclear membrane, 



