Fertilization in Pinus Sir obits. 457 
the chromosomes were completely fused in the reticula of the 
daughter-nuclei. One is reminded by these phenomena, of 
Strasburger’s (’ 92 ) remark, when he states that he accepts the 
view of a complete fusion of the segments into a network in 
the daughter-nuclei, and then asks if he must, therefore, 
conclude that the chromosomes in the following divisions do 
not correspond in material. 
Ruckert (’ 95 ) found that the chromatic portions of the 
conjugating nuclei in Cyclops not only remained distinct 
during the first division, but that two groups of chromosomes, 
representing respectively the maternal and paternal chromatic 
elements, could still be recognized after several divisions had 
taken place. In this case, however, the two groups do not 
fuse in the daughter-nuclei but a double nucleus is formed in 
the resting stage. In the same year Zoja (’ 95 ) observed that 
in Ascaris the maternal and paternal chromosomes remain 
entirely distinct during several successive divisions of the 
segmentation-nucleus. We have, then, in this second division, 
a further point in which fertilization-phenomena in Pinus 
correspond to those which occur within the ova of some 
animals. I have, as yet, made no attempt to obtain a com- 
plete series of stages in the development subsequent to the 
formation of the first. four nuclei of the proembryo. But, from 
a comparison of Fig. 79 b with 71, and 80 b with 64, one is 
led to expect that the third division following fertilization 
will correspond in all points with the second. It would be 
interesting to determine if two chromatic groups are character- 
istic of all the divisions which normally occur within the 
oosphere of Pinus , and I hope to be able, shortly, to 
investigate this question more thoroughly. 
The four Segmentation-Nuclei. 
As a rule these nuclei retain their position in the upper 
half of the egg until their growth is completed (Fig. 76). 
Here, again, as in the development of the two segmentation- 
nuclei, the steps described for the maturation of the egg- 
