138 SECRETS OF ANIMAL LIFE 
chromosomes, which probably bear respectively 
paternal and maternal hereditary qualities. Accord- 
ing to Professor Brachet and some other authorities 
the sperm-cell is not important in connection with 
the transmission of specific characters—that is the 
ovum’s role, but, in addition to its chief function 
as “an agent in division,” it may be credited with 
being the vehicle of minor personal features char- 
acteristic of the male parent. This view is a blow 
to proud fathers, but it is probably the exaggera- 
tion of an element of truth into a falsity. (2) The 
fertilization, as we have mentioned, restores the 
normal quantity of chromatin and the normal 
number of chromosomes. In some cases, especially 
among insects, it has been proved that there are two 
kinds of sperm-cells, one contingent with, and the 
other contingent without a special sex-chromosome, 
and that the sex of the offspring hangs on the 
fertilization. Thus an even number of chromosomes 
in the fertilized ovum may mean a female offspring, 
while an odd number may mean a male. In other 
cases, however, the sex of the offspring is determined 
by the physiological character of the egg-cell, 
quite irrespective of fertilization. Thus Professor 
Oscar Riddle has shown in pigeons that the eggs with 
less intense metabolism and greater storage capac- 
ity develop into females. (3) The entrance of the 
sperm-cell implies the advent of a minute body 
called the centrosome, a mountain-moving mouse, 
which divides into two, and plays an important part 
in the subsequent division, acting, as it has been 
