470 Ferguson. —The Development of the Egg and 
branes entirely disappear. The two chromatic groups remain 
distinct until the nuclear plate stage. 
The spindle of the first division following fecundation always 
lies between the conjugating nuclei and parallel with the 
outer, free surface of the sperm-nucleus. It is multipolar in 
origin and is probably derived equally from the paternal and 
the maternal nucleus. The spindle-fibres appear to arise by 
a rearrangement of the achromatic nuclear reticula and are 
evidently not the expression of a special kinoplasmic substance. 
After the formation of the daughter-nuclei, the greater portion, 
if not all, of these threads pass into the cytoplasmic network. 
During metakinesis and later stages this spindle may vary 
from a broad, multipolar diarch to a slender bipolar spindle. 
The chromosomes pass to the poles in the form of narrow U’s* 
No individualized centrosomes or centrospheres have been 
found to occur in connexion with the first division following 
fertilization. But the entire activity connected with this 
mitosis indicates that the sperm-nucleus, under the influence 
of the egg-cytoplasm, is the agent which initiates and controls 
the division. 
The two segmentation-nuclei present a reticulated structure 
in which the paternal and the maternal chromatin appear to 
be completely fused. They divide in the upper part of the 
egg, passing through practically the same steps as those noted 
for the first division. The two" chromatic spirems of each 
nucleus take up a position along the adjacent sides of the 
nuclei. A longitudinal splitting of the chromosomes first 
becomes apparent during an early stage in metakinesis. 
The four segmentation-nuclei attain full size while still in 
the upper part of the egg. As they pass to the base of the 
oosphere, fibres occur in the cytoplasm similar to the threads 
observed around the descending egg-nucleus. The steps in the 
division of these nuclei have not been carefully traced, but, 
from the stages observed, it is probable that this mitosis does 
not differ from the division of the two segmentation-nuclei. 
No cell-wall is laid down at the base of the oosphere, in the 
species of pines which we have studied, until after the eight- 
