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and of other related Primula Hybrids. 
As the spireme comes out of synapsis it exhibits a certain amount of 
approximation between its lengths, but by the time that the open spireme 
stage is reached the spireme is thrown into loops, the sides of which are 
widely separated, the only places of union between them being the points 
of intersection. Gradually the sides of portions of the looped spireme 
approach one another, and thus indicate, in the still continuous spireme, that 
association which will eventually result in the formation of the respective 
future bivalent chromosomes. The lateral association between the strands 
becomes increasingly more intimate. The spireme then segments. When 
the necessary blending of the two is accomplished, then the bivalent 
segment splits into its two univalent chromosomes. These retain their 
connexion during diakinesis and finally separate on the spindle of the first 
meiotic division. 
Thus Primula clearly illustrates the views held by Farmer and Moore 
( 11 ) regarding the telosynaptic arrangement of the univalent chromosomes 
in the spireme. It is evident that in the looping of the continuous spireme 
the future univalent chromosomes, which separate at the heterotype mitosis 
and are distributed between the two daughter nuclei, are arranged end to 
end, for each side of a loop becomes in process of time a univalent chromo- 
some. As the loops fold over and the sides approximate there is secondarily 
a greater or a less degree of parasynapsis between them before their ultimate 
separation. 
This telosynaptic origin of the bivalent chromosome is wonderfully 
clearly shown in Primula , both on account of the sharp definition of the 
spireme and also owing to the fact that in two of the Primulas examined 
there is no second contraction, so that the whole process of association, 
fusion, and splitting apart of the univalent spiremes can be traced in perfect 
sequence. 
The univalent spireme of Primida is of even thickness and its outline 
so definite that the places where it forms a bivalent association are most 
obvious. This gives it a great advantage over some other forms in which 
the spireme is apparently very viscous, which makes it impossible to decide 
whether the strands are of the bivalent or of the univalent order, for they 
may be stretched into a fine thread or contracted into a broad ragged band. 
Besides being regular in thickness, the spireme of Primida is almost 
invariably homogeneous. It has been shown that the spireme is univalent 
in nature, so that in the rare cases when fission in its substance has been 
seen it must be the premature appearance of the fission which will divide 
the univalent chromosomes at the homotype division. 
Secondly, as regards the character of the nuclei of hybrids. As a rule 
hybrids are sterile, or partially so, but it is not a feature peculiar to them, as 
it has frequently been shown that pure races may be also largely sterile. 
Geerts (19) found that 50 per cent, of the pollen-grains of O. Lamarckiana 
