BLEPHAROPLAST PARABASAL KINETOPLAST 119 



mitotic division of the nucleus occurs without any centrosomes at the 

 poles of the spindle. Instances are known, however, in which the blepharo- 

 plasts which are separate from the nucleus occupy during nuclear division 

 positions upon the spindle which centrosomes would be expected to 

 occupy. Such an example is seen in the division of Oikomonas termo 

 described by Martin (1912) (Fig. 135). 



In the case of Proivazekella lacertce, which has an axoneme originating 

 in a blepharoplast on the nuclear membrane, the nucleus has one or more 

 parabasals surrounding it. When division of the nucleus takes place, 

 the daughter blepharoplasts occupy the poles of the spindle and mitotic 

 division takes place, as in Heteromita and Cercomonas. The parabasal, if 

 there is a single one outside the nucleus, becomes elongated and divided 

 into two parts, one of which passes to each daughter nucleus. When there 

 are several parabasals they separate into two groups without dividing 

 individually, very much like the behaviour of mitochondria during division 

 of spermocytes in the process of spermatogenesis (Fig. 254, s-x). 



The function of the centriole in nuclear division has been discussed 

 above. It will be seen that in Heteromita uncinata, Cercomonas longicauda, 

 and other forms in which the blepharoplast occurs on the nuclear mem- 

 brane, and in certain cases where it is separated from the membrane, 

 the daughter blepharoplasts occupy during nuclear division the same 

 positions that the daughter centrioles are said to occupy. It is claimed 

 that as the centriole is functionally a centrosome, the blepharoplasts of 

 flagellates must also be centrosomes. It is further assumed that, in 

 those cases in which the blepharoplast occupies a position in the cyto- 

 plasm apart from the nucleus, it represents a centriole or centrosome 

 which has left the nucleus or is the result of division of the centrosome 

 into two parts, one of which remains in the nucleus and still functions 

 as a centrosome during its division, while the other has left the nucleus 

 to become a blepharoplast. 



The whole subject of the relation of blepharoplasts to centrosomes 

 is a very complex one, and depends largely on the exact definition of a 

 centrosome. Some observers definitely assert that the blepharoplast is 

 a centrosome. Minchin (1914), for instance, stated that in his opinion it 

 was a well-established fact that in a great many cases blepharoplast and 

 centrosome were one and the same body. It seems difficult to doubt 

 this in view of the fact that in the developing spermatozoon of higher 

 animals the axial filament of the tail which corresponds with an axoneme 

 is known to be formed as an outgrowth from the centrosome. In fact, the 

 tail with its axial filament arising from the centrosome is exactly com- 

 parable with the flagellum with its axoneme and blepharoplast. 



The question of the nature of the numerous blepharoplasts possessed 



