308 CONCLUDING CHAPTER 
gametes, as well as to the mass of cells to which the 
zygote (in the strictest sense) eventually gives rise. 
In the simplest forms, such as the green algz, the cell- 
and nuclear-fusion constituting conjugation are imme- 
diately followed by fusion of the chromosomes, an 
event which we have seen to be the first step towards 
a reduction in the number of these bodies. In the 
higher plants, by delaying this fusion of chromosomes 
until many cell generations later than the fusion of the 
nuclei, the advantages associated with the possession 
of a double nucleus have been obtained for a large and 
complicated mass of cells. And this mass has gradu- 
ally advanced in organization and relative importance, 
until ultimately the x-generation has been reduced 
almost to the vanishing point. 
The sex-phenomena of the higher animals can most 
readily be brought into line with those of the higher 
plants if we consider that in animals the spore and the 
gamete are identical; the x-generation is here con- 
densed into the smallest possible limits—namely, those 
of a single cell. 
A female animal produces ova, and a male produces 
spermatozoa. Similarly, we may regard as a female 
plant one which produces only the larger variety of 
spores from which ova arise ; and we may regard as a 
male plant one which produces only pollen. It is 
much more usual to find a flowering plant bearing both 
pistils and stamens, and producing both large and small 
spores. Such an organism is described as herma- 
phrodite—bearing both sexes. Among animals ex- 
amples of hermaphrodite species are also not infrequent, 
