the Embryo-sac Mother-cell of Lilium, 351 
example, would not be regarded by the writer as spirems, much less as 
bivalent spirems, but merely as a network — a number of scattered chromatin 
lumps connected by linin threads. It seems to me also that one may just 
as well interpret the cytoplasm of Overton’s Fig. 13, PL II, as consisting of 
bivalent ‘ heterogeneous ’ spirems as to apply such a designation to the 
nuclear structures just mentioned. 
The foregoing results of observations upon the prophases of the hetero- 
typic mitosis in the megaspore mother-cell of Lilium may, therefore, be 
briefly summarized as follows : — 
1. Previous to synapsis a single nuclear thread is developed, which, in 
many cases, can be demonstrated clearly as a definite spirem with somewhat 
regular and uniform chromatin granules. 
2. There is no union side by side of two distinct chromatin spirems 
prior to or during synapsis. Synapsis is regarded as a normal process, but 
the greater compactness of the balled-up mass may be due partly to the 
reagents. 
3. The hollow spirem following synapsis is double, due to a longitu- 
dinal fission, which, as a rule, becomes completely obscured before the cross 
segmentation. 
4. The segments arranging themselves in pairs to form the bivalent 
chromosomes were placed end to end in the spirem. 
5. The separation of the members of each bivalent in the first mitosis 
is, therefore, a cross segmentation. The heterotypic mitosis is thus 
reductional, and, if one chromosome differs from another potentially or 
otherwise, it is also qualitative. 
6. In the pre-synaptic phase, that the chromatin may appear as larger 
lumps instead of smaller and more uniform granules, has been suggested as 
being due in part to the fixing fluids, the finer more uniform granules being 
nearer normal. The wide divergence of the halves of the chromatin thread 
appearing occasionally in the stage of the hollow spirem may also be due 
in part to the reagents. 
February 15, 1909. 
Publications referred to. 
Brown, William H. (’08) : The nature of the embryo-sac of Peperomia. Bot. Gaz., xlvi, 445-60, 
1908. 
Gates, Reginald R. (’08) : A study of reduction in Oenothera rubrinervis. Bot. Gaz., xlvi, 
1-34, 1908. 
Lewis, Isaac M. (’08) : The behaviour of the chromosomes in Pinus and Thuja . Ann. of Bot., xxii, 
5 2 9-5 6, i9° 8 - 
Mottier, D. M. (’07) : The development of the heterotype chromosomes in pollen mother-cells. 
Ann. of Bot., xxi, 309-47, 1907. 
