642 Wisconsin Academy of Sciences, Arts, and Letters. 
second contraction figure would necessarily follow the con¬ 
tinued shortening and thickening of the continuous spirem. It 
is my opinion that the second contraction figure arises as a nec¬ 
essary stage in the shortening of the elongated post-synaptic 
spirem to form the short heterotypic chromosomes. 
That part of Janssen’s (43, 44) hypothesis of a “tension 
nucleaire” which assumes the spirem to be attached in places to 
the nuclear membrane may possibly be applicable to the second 
contraction stage in Smilacina. Still that any tension exists 
in the nuclei of Smilacina at this stage seems improbable. The 
curvature of the coils and loops of the spirem is too great to be 
consistent with any great tension. Further this hypothesis as 
suggesting a method of segmentation seems to be superfluous 
for in ordinary mitoses no such mechanism is necessary for the 
segmentation of the spirem. 
Overton’s (7) suggestion that in plants with short chromo¬ 
somes the second contraction stage is inconspicuous or lacking 
probably should be limited to refer to those forms whose nuclei 
have a relatively small amount of chromatin as is the case in 
Oalycanthus and Thalictrum. 
Strasburger’s explanation (98) that the second contraction 
figure is formed around the nucleolus for the possible purpose 
of obtaining nutriment from it, fails with Smilacina for here 
several nucleoli are present and but one center of aggregation. 
The nucleoli are probably more frequently to be found outside 
of the contraction figure than included within it. The sugges¬ 
tion of Strasburger that in nuclei with several nucleoli several 
centers of aggregation or none could be expected, finds no sub¬ 
stantiation in Smilacina for I have never observed more than 
one center of aggregation and have never observed nuclei of this 
prophase in which it was lacking. The second contraction figure 
is here quite unrelated to the position of the nucleoli. 
Gates’ (30) conception that the second contraction stage cor¬ 
responds to the “bouquet stage” of Eisen seems based on the apr 
proximate time of its occurrence. In the “bouquet stage” the 
chromosomes become definitely oriented in respect to the cen- 
trosome. The stage is commonly described as occurring im- 
