ORIGIN OF MYCETOCYTES IN PSEUDOCOCCUS. 289 



It might be supposed that even during the resting phases the 

 sizes of the fusing nuclei would suffice to identify them. And 

 indeed it seems well established that when the two types of 

 nuclei are at precisely the same stage, that of the polar nucleus 

 derivative with its 15 chromosomes is slightly larger than a 

 cleavage nucleus with 10. But it is practically impossible to 

 exactly identify the phase of the nucleus during its preparatory 

 phases. At the same time it has already been noticed that varia- 

 tions in the size of any one type of nucleus are extreme. The 

 changes in size seem directly related to the condition of the con- 

 tained chromatinic material and are such that the nuclear 

 volume is smallest just after the formation of the nuclear wall at 

 telophase, and largest immediately before the dissolution of the 

 nuclear wall prior to the following division. Thus the increase 

 in size of the female pronucleus between the telophase of the 

 last maturation division and the time when the chromosomes are 

 again almost fully condensed before the first segmentation 

 division, are very considerable (Figs. 8a and 1 1, '23). Changes of 

 size almost as great can be observed in the polar bodies prior to 

 the formation of the polar nucleus and the polar nucleus deriva- 

 tives. It is therefore manifestly impossible to arrive at any con- 

 clusion regarding the nature of fusing nuclei by simply comparing 

 their size when it is considered that a further complication arises 

 from the fact that apposing nuclei may be at entirely different 

 phases (Fig. 7 'a and 10). 



In spite of the very different phases that two or even three 

 apposed nuclei may be in, it is apparent that a normal plate of 

 chromosomes, which represents the summation of the numbers 

 contained in each of the fusing nuclei, is finally attained. This 

 may happen only when all of the nuclei are in a very definite 

 generation of cells as has been pointed out in regard to the ques- 

 tion of the number of divisions undergone by the polar nucleus. 

 It is also a consequence of these observed facts regarding the 

 varying phases of apposed nuclei, that the chromosomes of one 

 or two of the nuclei will reach their full condensation prior to 

 those of the other nuclei involved. Those first evolved must 

 therefore be subjected to a suspension of further activity until 

 those lagging behind have caught up. All of my figures make it 



