EUPLOTES WORCESTER!: 11. 317 



It. appears to consist of a homogeneous fluid, no stmeture of any kind 

 being visible; but it is probable that a linin network still exists there, 

 masked by the stain. 



I have given the name reconstruction plane to the clear distal plane. 

 It follows the solution plane abruptly, without any noticeable transition 

 region between the stained and clear zones. In many cases no structure 

 whatever is visible with a magnification of 1,600 diameters in the central 

 side of the reconstruction plane. On the distal side, fine fibrils of chro- 

 matin appear which are connected with the reticulum of the distal part 

 of the nucleus. These increase in thickness and number very abruptly, 

 making thus a quite definite distal limit to the plane. It is evident that, 

 while reconstruction of the chromatin commences in the region I have 

 termed the reconstruction plane, it is not limited to this, but proceeds 

 most actively in the region just distal to it, where the chromatin fibers are 

 so suddenly thickened. The anterior portion of the plane is in fact the 

 region where solution has been completed and chromatin (in a stainable 

 form) has entirely disappeared, wliile in the posterior part of the zone 

 chromatin is appearing. 



Although I have failed many times to see any structures in the central 

 side of the reconstruction planes, on other occasions I have obs'erved a 

 reticulum of extremely fine, delicately staining fibrils occupying all 

 parts of the plane. These seem to be true linin fibrils, for it is at their 

 nodes that the graniiles of chromatin first appear, and the chromatin 

 reticulum appears to be built upon them. I believe that the linin net- 

 work, even though often invisible, is always present in all parts of the 

 reconstruction band. 



The staining power of the reconstructed chromatin is considerably 

 greater than that of the portion not yet altered. In judging the depth 

 of stain, care must be taken to allow for the concentration of the nucleus 

 which follows soon after the reconstruction bands pass. However, it is 

 true that in nuclei in which concentration seems not to have begun the 

 new chromatin stains much more vividly than the old. It frequently 

 forms numerous masses of quite large size at the nodes of the reticulum, 

 although just as often the chromatin knots are not present. 



The margin of the undissolved (central) reticulum is usually abrupt. 

 It often appears as in Plate IV, figure 6, closed across the face of the 

 solution plane. On the other hand, Plate V, figure 13, shows a nucleus 

 in which the chromatin has evidently begun to dissolve a little distance 

 in front of the dark solution plane. 



The planes of solution and reconstruction are of nearly equal thickness, 

 their combined thickness being about the same as the width of the 

 jmcleus. 



The two reconstruction bands pass toward the center of the mega- 

 nucleus at equal rates until they finally meet. (Plate V-, figure 14; Plate 

 ■ VI, figures 18, 80.) The two solution planes then unite, and presently 



