of Fertilization in A ngiosperms. 703 
present, a double process is included under the general term 
fertilization. Characters from both parents are transferred 
to the offspring by amphimixis, and the development of the 
fertilized egg-cell is secured by the presence of a growth- 
stimulus. 
If we now inquire into the machinery by which these results 
are attained, we find that the act of fertilization is remarkably 
uniform in all organized beings. It consists in a fusion of two 
cells to form a new one, which then divides and ultimately 
gives rise to an individual whose characters are intermediate 
between those of its parents. This is fertilization in the 
concrete sense. Its phenomena supply a material basis for 
the general laws of heredity to which I have just referred. 
When the act of fertilization is studied in detail, certain 
features are found to be general. The male cell is usually 
small, and the nucleus forms the most considerable part of it. 
The cytoplasmic elements are greatly reduced. When the 
male and female cells fuse, the union of their nuclei is the 
most characteristic feature of the process. Both are generally 
in the resting state at the time of fusion, but though they 
commonly unite in that condition so far as to enclose a single 
cavity, yet it very often happens that fusion is not complete 
until the first karyokinesis has taken place 1 . The male and 
female chromosomes can frequently be distinguished in the 
equatorial plate, and it is not until a segment of each has 
travelled to either pole, and the daughter-nuclei are in process 
of construction, that the chromatic elements from the male 
and female nuclei are really united. Boveri (18) does not 
consider the act of fertilization complete until the first 
karyokinesis after conjugation is accomplished (p. 416 ). 
There is a double advantage in adopting this view. We 
are secure that the chromatin-fusion has actually taken place, 
and the occurrence of the first division in the egg shows that 
the stimulus to development is also present. 
The arguments which have led most biologists to consider 
1 See the discussion in Boveri’s article on Fertilization ( 18 , pp. 403-5), and 
the literature there referred to. Also Guignard ( 23 , p. 199). 
3 A 
