448 Ferguson . — The Development of the Egg and 
the oosphere of the four nuclei of the pollen-tube, but he 
could not distinguish between these after their entrance into 
the egg. Blackman confirmed Dixon’s observations as to the 
passage of these nuclei into the oosphere, and believed that 
the cytoplasm of the ‘ sperm-cells ’ passed into the egg along 
with the sperm-nuclei, but he was unable to demonstrate 
the fact. There can be no doubt that the cytoplasm of the 
sperm-cell enters the egg in Pinus Strobus (Fig. 39). This 
cytoplasm very soon fuses with that of the egg, and the 
larger sperm-nucleus moves towards the nucleus of the 
oosphere ; the other elements from the pollen-tube remain 
for some time in the upper part of the ovum. There is no 
evidence that the sperm-nucleus increases in size after enter- 
ing the oosphere ; neither is there an increase in stainable 
substance, but, on the contrary, the nucleus loses its dense 
structure ; and occasionally a nucleolus becomes apparent 
within it. (Compare the sperm-nuclei in Figs. 39 and 40 with 
those in Figs. 42-50.) 
There is every indication that the movement within the egg 
of the sperm-nucleus which becomes active in fertilization is 
both rapid and direct. It almost invariably traverses the 
shortest distance between its point of entrance into the egg 
and the egg-nucleus. The relative position which the con- 
jugating nuclei may occupy with reference to the major axis 
of the oosphere varies considerably, but always bears a definite 
relation to the position of the neck-cells. When these cells 
are directly above the centre of the oosphere, the sperm- 
nucleus comes into contact with the upper part of the egg- 
nucleus (Figs. 41, 44, 45, 48, and 50) ; but if the neck be 
excentrically placed, the sperm-nucleus will be found against 
one side of the oosphere-nucleus (Figs. 43, 46, and 47). It 
has not been observed beneath the egg-nucleus as figured by 
Coulter (’97) in Pinus Laricio. Neither is there a bulging 
of the egg-nucleus towards the sperm-nucleus, nor do the 
sexual nuclei ever approximate in size as shown in this same 
figure of Coulter’s ; but a somewhat similar figure has been 
observed in Pinus Strobus after the first division of the 
