540 The Ohio Naturalist. [Vol. IX, No. 8, 



recognizable protochromosomes as in Thalictrum, Agave, and 

 various other plants. 



Following this stage the complicated spirem is formed, which 

 gradually thickens until its continuity can be traced with 

 comparative ease, although it is very irregularly looped and 

 twisted (fig. 9). At this stage the so-called synizesis probablv 

 occurs. This varies from slight contraction to a dense massing 

 in the center or side of the nuclear cavity. The nucleolus may 

 or may not appear free from the mass (fig. 8). Sometimes 

 series of sections, apparently of the proper stage, do not show 

 synizesis, while in others contractions are present even in well 

 developed spirems. 



The spirem continues to thicken and the irregular twisting 

 and winding becomes less complicated, with a strong tendency 

 to form loops, the crossing threads producing a dense mass in the 

 center (figs. 10, 11). This arrangement of the loops with 

 crossing in the center has been noted in other members of the 

 lily famih^ 



No trace could be found of double granules or a split in the 

 spirem. This, however, may have been due to the staining. 

 The linin and chromatin granules appeared quite distinct in the 

 earlier stages (figs. 5a, 9a) but with the twisting and winding 

 prior to the formation of loops, they stain much darker and more 

 uniformly until differentiation finally disappears. The twisting 

 of the spirem now becomes gradually simplified until there are 

 approximately eight loosely rounded loops, the eight incipient 

 chromosomes, corresponding to the reduction number of chromo- 

 somes (figs. 12,13 ). These loops thicken and condense until 

 there are clearly eight loops radiating from the center, with the 

 looped ends pointing outward toward the nuclear wall (figs. 14, 

 15) . The eight chromatin loops were distinctly seen and counted 

 a large number of times. 



The arrangement of the spirem into loops, corresponding in 

 number to the reduced number of chromosomes and their 

 subsequent separation and massing to form the chromosomes 

 was mentioned by Schaffner in his paper on Lilium philadel- 

 phicum. He found that the "twisted chromatin band arranges 

 itself so as to form twelve loops, the heads of the loops being 

 close to the nuclear membrane." This arrangement was also 

 found by Brown in his study of the embryo-sac of Peperomia. 

 In this case he finds that after the looping becomes more pro- 

 nounced, the spirem .segments, each loop giving rise to a chromo- 

 some. He draws the conclusion that chromosomes are, therefore, 

 formed by the coming together, side by side, of parts of the 

 spirem that before were arranged end to end. Gates notes a 

 somewhat similar condition in Oenothera rubrinervis, in which 



