358 - BULLETIN OF THE 



process is, however, too slow to be directly observed in the living nucleus ; 

 only a series of successive drawings makes it apparent. The course of 

 the filaments becomes more generally perpendicular to the major axis 

 of the nucleus. Toward the end of this phase the sharp contour, which, 

 in the first phase, marked the place of the nuclear membrane, is no 

 longer present, but there is a clear zone around the nuclear figure, which 

 is visible in living, as well as in hardened cells. This, although possi- 

 bly more extensive on hardened preparations, is not, then, solely artifi- 

 cial (Mayzel). In preserved preparations delicate branched cords may 

 be seen to connect the periphery of the nuclear figure with the cell 

 plasm. 



Phase 3. Star form of the mother nucleus. Just how this phase is 

 produced from the preceding cannot be determined on living nuclei. 

 Flemming believes it is accomplished through intermediate stages, the 

 most characteristic of which is the crown form. In the latter the course 

 of the filaments is almost exclusively radial, and in many cases a central 

 space is left entirely free ; both at the periphery and near the centre the 

 filaments form loops, and thus show that they are more or less continu- 

 ous. This hollow sphere of looped filaments gradually affects an ar- 

 rangement in a single plane (not that of the approaching division), and 

 therefore is more directly comparable with a ring, or, if the centre is not 

 hollow, with a disk. The peripheral loops of this crown now break 

 through, so that there are twice as many free ends as there formerly 

 were peripheral folds. The rupture need not necessarily be at the apex 

 of the loop. Thus the crown form passes into the star form. Already 

 in this stage a dicentric grouping is sometimes to be observed in the 

 stellar figure, since the loops which correspond to the division poles are 

 the first to be ruptured, those near the equator the last. Very rarely 

 there is a genuine double star with completely separated centres.* 



Another remarkable change takes place either at the end of the pre- 

 vious, or during the present stage. The filaments split lengthivise each 

 into two. This is quite typical, at least for Salamandra. After the rup- 

 ture of the peripheral loops the free ends of the split filaments diverge, 

 and thus give rise to a fine-rayed star. This fission of the nuclear fila- 

 ments is not the result of the use of reagents, as it has been seen in the 

 living cell also. It has been observed to remain in this condition for 

 two hours, and meantime the stellar figure undergoes a series of slow 

 changes of form — a sort of systole and diastole — which affects the 



* This separation, I would add, is not to be mistaken as equivalent to the division 

 of the equatorial plate. 



