524 CANNON: STUDIES IN PLANT HysrIDs: 
preparation. On the other hand instances were observed, like f. 8, 
in which a reticulum was being formed from the condition as just 
described. The exact fate of the chromatin was thus not deter- 
mined. 
The association of chromosomes in pairs in the early history 
of the reproductive cells recalls the similar condition in animals 
as given by Montgomery * and Sutton.+ But the significance of 
the association in hybrids is not entirely clear, since with Mont- 
gomery’s hypothesis in mind that in pure races the two chro- 
mosomes of each pair are of different parentage, it seems difficult 
to conceive of Sutton’s as applied to hybrids, that the members 
of each pair cover the same field of development ; because in hy- 
brids the latter can only be true in a broad way, depending ap- 
parently upon the affinities of the pure parents of the form. It 
may be, however, that the differences between the chromosomes 
of any pair in hybrids capable of forming functional spores are so 
slight that union is possible even if the potentials of the chromo- 
somes are not identical. . 
After the sporogenous cells are cut off there ensues a long 
period of growth during which the nucleus of the young spore 
mother-cell undergoes characteristic changes. The chromatin of 
the nuclear reticulum becomes gathered to one side of the nucleus 
and the contracted condition known as synapsis results. The 
preparation for synapsis takes place at an early time in the history 
of the spore mother-cell, and the portions of the nuclear changes 
resulting in synapsis which were seen may be briefly described. 
The delicate reticulum which extends through the nuclear vacuole 
of the resting nucleus becomes so changed that small masses of 
chromatin of unequal form and size are found scattered along its 
meshes, more especially in the peripheral part of the nucleus. 
These masses are arranged in lines which often radiate from the 
nucleolus as a center; the linin threads which connect the masses 
may be seen for a considerable distance from them extending into 
the nuclear vacuole. From a position extending over the entire 
periphery of the nucleus the chromatin becomes gathered to 
*Montgomery, T. H. The heterotypic maturation mitosis in Amphibia and its 
general significance. Biol. Bull. 4: 259. 1903. 
f Sutton, W. S. On the morphology of the chromosome group in Brachystola 
magna. Biol. Bull. 4: 24. 1902. 
