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1903] PRIMARY NUCLEUS IN SYNCHYTRIUM 4 1 1 



many others to view. It is particularly noticeable that no 

 curving or looping is seen, the threads ever remaining straight 

 and intersecting in acute angles. 



Judging merely from the size of the nuclei, the critic may 



assert that 7?^. 7 represents a stage intermediate between those of 



^^s. I and J, a criticism that is fully met, however, by further study 



of the figures, since neither the condition of the nuclear membrane 



nor of the nucleolus admits of the intercalation of any such con- 

 dition as that shown in fig. 7. Moreover, the sorus is at its 

 maximum when presenting the structure shown in fig. y, which 

 would not be the case if this were intermediate between figs, i 

 and J. Even if no more advanced stages were discovered, we 

 see no escape from the conclusion that fig. 7 represents the 

 spirem and is a later development from such structures as are 

 shown \Vifigs. 7, ^, J, etc. The fact that/^. 6 is slightly smaller 

 than fig. J is explicable by the assumption that it is derived 

 from a smaller resting nucleus. Fig. 6 clearly represents a stage 

 early in the dissolution of the nuclear membrane, likewise early 

 in spirem formation. It must lie between _/f^.y. 5 and 7, and that 

 without contradicting the general fact of a nuclear shrinkag 

 throughout the mitosis. Figs. 8-10 represent a progressive series 

 of stages clearly more advanced than figs. 4-6. In these the 

 boundary region is practically unchanged in character, though 

 continually contracting with the diminution of the nucleus. The 

 spirem threads as shown in fig. 8 become slightly thickened, 

 apparently by longitudinal fusion of separate rods. There is a 

 tendency of the chromatin to accumulate in masses, though never 

 partaking of that peculiar characteristic lumpy appearance shown 

 fiS^- J, 4- Vestiges of the nucleolus remain as in fig. 7 

 throughout further stages of mitosis. Fig. p shows, in a much 

 more pronounced way, how the threads coalesce as they meet m 

 the center. Meanwhile the size of the nucleus decreases. In 

 Jg. 10 there is a distinct indication of an arrangement in spindle 

 form, though many strands remain as yet apparently in no way 

 connected with the developing spindle. From this series and 

 numerous other similar stages seen by the writers, there remams 

 no doubt that from the spirem the nucleus passes to a definite 



m 



