704 Sargant.—Recent Work on the Results 
the union of chromosomes as the agency by which the parental 
qualities are united in the offspring, are too familiar to need 
repetition. I need only refer to Boveri’s essay on Fertilization 
( 18 , pp. 417-23) and Weismann’s Germ-Plasm ( 45 , pp. 23-35). 
We must consider the process of amphimixis as bound up with 
the act of nuclear conjugation. 
It is less easy to localize the agent which carries with it the 
impulse to growth. In some animals it appears to reside in 
the centrosome belonging to the sperm-nucleus (Boveri, 13 , 
pp. 427-9) h Strasburger ( 11 , p. 307) conjectures with much 
probability that in the higher plants the male cytoplasm may 
carry the growth-stimulus with it. If this be so, we have in 
the higher plants a compound process which it seems most 
convenient to call fertilization, including two subordinate 
processes. These are (1) amphimixis, or the union of parental 
qualities in the embryo, and (2) a growth-stimulus which 
ensures that development of this embryo shall at least begin. 
Fertilization thus defined is effected by the fertilizing act, 
which also includes two distinct phenomena—nuclear conju¬ 
gation and union of the cytoplasmic constituents. There is 
good reason to suppose that the process of amphimixis is 
inseparably connected with the act of nuclear conjugation, 
and very possibly there may be a similar connexion between 
the growth-stimulus and the fusion of male cytoplasm with 
that of the egg-cell. 
We have hitherto been considering the fertilization of the 
egg-cell by the male cell from the pollen-tube, the result of 
which is a normal embryo. Let us now apply the same 
touchstones to the triple fusion—often regarded as a second 
act of fertilization, which produces endosperm-tissue. Here 
we have an undoubted male nucleus fusing with two others. 
Of these the upper polar nucleus is the sister of the egg- 
nucleus. It can hardly be regarded otherwise than as a 
female nucleus. There is in this union then, a male and 
a female element. Both are perfectly normal, formed by 
a series of reduction-divisions, and containing the reduced 
3 See also an article in ‘ Nature ’ for April 5, 1900, p. 551. 
