1918] WENIGER—FERTILIZATION 265 
in contact with them (fig. 8). A spireme is then formed in each 
polar nucleus also (fig. 9), and the nuclear membranes disappear 
at the point of contact of the nuclei. The lower polar nucleus is 
usually a little larger than the one coming from the micropylar end 
of the embryo sac. The male nucleus is at the left in fig. 9. 
Segmentation of spiremes occurs so that on the spindle (fig. 19) 
the chromosomes are extremely long and U-shaped. The number 
of segments is difficult to ascertain, but it approaches the 3x 
number. The division is accomplished by a longitudinal splitting 
_of chromosomes, producing in the anaphase a mass of long bent 
segments that cannot be counted with any satisfaction. 
There is a striking difference between the first division of the 
fertilized egg and that of the endosperm nucleus. The former is 
characterized by shorter straighter chromosomes, a pairing of 
chromosomes, and a subsequent transverse breaking of each pair to 
form 4 segments, of which 2 go to each pole. The division of the 
endosperm nucleus resembles the ordinary vegetative division by 
means of a longitudinal splitting of chromosomes. The number of 
chromosomes is 3x. Since previous cytological work has not 
covered the necessary phases, it is possible that the description of 
the behavior of chromosomes during the first division of the 
fertilized egg here given may apply quite generally to angiosperms. 
A longitudinal splitting of chromosomes on the equatorial plate 
would bring about the same result in that the 2x number of chromo- 
somes goes to each of the daughter nuclei; but the supposition of a 
longitudinal splitting would not account for the situation described. 
If a longitudinal splitting should occur before the transverse break- 
ing, rather than a pairing of chromosomes, the resulting number 
would be 96 rather than 48 segments. 
The 3 phases of fertilization, union of cells, union of nuclei, and 
union of chromosomes, occur in rapid succession in animals, since 
the reduction division immediately precedes fertilization. In plants 
the 3 processes may be separated for a longer or shorter period. 
In the rusts there is a long gap between the union of the gametes 
at the base of the aecidium and the nuclear and chromosome 
conjugation. In some of the green algae, such as Oedogonium, the 3 
come close together, since reduction follows soon after fertilization. 
In the brown algae the 3 are also close together, but reduction 
