386 BULLETIN OF THE 



rectly the nuclear plate, in which they lose their individuality. This 

 migratiou and confluence of the coarse granules is accompanied (always?) 

 l)v a marked contraction of the nucleus. 



In the division of the nuclear plate and the separation of its halves, 

 there appear first a narrow dark line through the middle of the band 

 (the disk seen edgewise), and then several detached, lenticular clear spaces, 

 which at length become confluent and thus effect a complete separation 

 of the halves. The latter move apart, rapidly at first, afterward with a 

 gradually retarded motion ; they become thicker, but less definitely out- 

 lined, the farther they move away from each other. They remain united 

 more or less by irregularly placed bands of threads, which for an instant 

 may form a bundle of parallel striations. Usually the nuclear plates 

 remain parallel, but in one case (Fig. 7) it was observed that the central 

 portions of the disks became widely separated while their peripheries still 

 remained close together.* 



During the latter part of the migration of the halves of the nuclear 

 plate, the old nucleus (its outline is no longer sharply distinguishable 

 from the enveloping protoplasm) undergoes a change of form and size. 

 It elongates, then it becomes broader till it sometimes touches the wall 

 of the cell ; but later its diameter undergoes a considerable reduction. 

 The nucleus finally becomes cylindrical, and at the same time the halves 

 of the nuclear plate become gradually rounded, and may now be called 

 secondary nuclei. Still later, minute granules in active motion are seen 

 to make their way toward the middle of the space between these two 

 secondary nuclei. They arrange themselves in a transverse layer, — the 

 beginning of the cell plate. Whence they arise is uncertain, but since 

 they move in all directions it is hardly possible that they glide along 

 invisible filaments stretched between the two secondary nuclei. 



In Crinura asiaticum Treub has seen the nuclear mass diff'erentiatcd 

 into rods (Fig. 27),t instead of granules, from which the nuclear plate 

 is formed. The homogeneous condition of the nucleus before the forma- 

 tion of the nuclear plate is far from being general. 



Treub disagrees with Strasburger as to the methods in which the cell 



* Were it not that Trenb's sketches presented in this case stages quickly succeed- 

 ing each other (Figs. 7^ to 7^ = 20 inin.), T should be inclined to think that his Fig. 1*^ 

 was the representation of a singh^ annular nuclear disk seen somewhat obliquely- 

 The signs of division shown in Fig. 7^ seem to preclude that view. I am induced by 

 these observations to again call attention to Fig. 24 of Bobretzky's ('76) paper, and 

 to admit that possibly a similar condition to that seen by Treub is the basis of this 

 ligure, which I have endeavored to explain in quite another manner. 



t Compare Strasburger '77, Taf. XXXIII. Figs. 55-58. 



