STUDIES OF AMITOSIS 493 



two different ways, naniel}': (1) The division of nucleus without 

 that of the cell-body, or (2), by the fusion of two or more cells. 

 Although the spherical cells of adipose tissue are usually altered 

 by pressure into irregular shapes, no one has ever detected any 

 sign of their fusion, and therefore the multinucleate condition 

 in this case must be regarded as due to the other method. 



If the adipose tissue containing bi- and multinucleate cells is 

 carefully examined, the fact maj^ be noticed that although no 

 mitotic figures are observable, not a few of the nuclei show such 

 figures as might be interpreted as various stages in the process 

 of amitosis. Since no other way of producing multinucleate cells 

 is possible, we should conclude that this kind of nuclear division 

 is responsible for such condition of the cell. 



A number of possible stages of amitosis observed in adipose 

 cells of Pieris larvae are figured. Figures 17 to 19 show what 

 appears to be the ordinary process of the amitotic nuclear divi- 

 sion. The nucleus first elongates, and then a constriction takes 

 place across its longitudinal axis. It may be described as a de- 

 velopment of a fold or in-pushing of nuclear membrane along 

 that line. The two parts of the nuclei are apparently distinguished 

 by a slight line before they separate. It is difficult to say whether 

 this line represents the developing new nuclear membrane or is 

 an optical image due to the constricted condition of the nuclei. 

 When the two daughter nuclei become separate, a sort of inter- 

 nuclear bridge, appearing as a strand of fibers, may sometimes 

 extend from one nucleus toward the other. This is considered 

 by Nemikoff ('03) as representing a special substance (inter- 

 nuclear substance), the significance of which is not yet under- 

 stood. The two parts of a dividing nucleus are not always of 

 equal size. Figures 20 to 22 represent cases in which one of the 

 parts was smaller than the other. An extreme case of this 

 nature is shown in figure 23, in which one is more than twice as 

 large as the other. Very rarely, constrictions may take place 

 at more than two places in the nucleus, in the case where the 

 latter is long and slender. Such a case is shown in figure 24. 

 It seems that such nuclei may divide almost simultaneously 

 into more than three daughter nuclei. 



