460 
Heredity and Sexuality. 
more or less complete suppression of the one kind of sexual appa- 
ratus in favour of the other, which consequently develops the more 
fully. The embryos of vertebrate animals are at first hermaphro- 
dite — a condition which is very commonly permanent amongst inver- 
tebrates, and is occasionally more or less so in the case of vertebrates. 
In plants, hermaphroditism is the rule the unisexual condition the 
exception. 
If the proportions of the sexes at birth be taken as a standard, it 
is found that normally the two sexes about balance each other in the 
case of the human species and of the domesticated animals, though 
with a slight predominance of males. Statistics of the European 
countries give an average of 105 boys born for every 100 girls. 
According to M. . Cornevin's observations, the ratios in the case of 
farm animals are : — horses, 101 males per 100 females ; cattle, 104*6 
males; sheep, 1 15*4 ; pigs, 104 - 9. Change in the environment 
appears to be one of the most potent causes in the determination of 
sex, and, as regards the human race, observations on this point are 
easily made. In hot countries to which white people have migrated 
there is a preponderance of girls at birth. Thus, in Java, of 7 
births amongst Europeans, 5 are girls and 2 boys ; in Yucatan 
of 10 births, 8 are girls. Horses equally serve to afford evidence 
that, in an environment different from their native one, there is an 
excess of female births. At the French national horse-breeding 
establishment at Pompadour, European-bred animals are mated 
with Arabs, imported direct from the East. M. Relier, veterinarian 
to the establishment, has drawn up the following table : — 
Pure-breds and Anglo-Arabs, 
Arabs, born of parents 
born of parents of European 
imported from 
Years 
origin 
the East 
Colts 
Fillies 
Colts 
Fillies 
1873 
7 
3 
1874 
4 
6 
1875 
6 
4 
5 
1876 
9 
1 
6 
13 
1877 
7 
5 
10 
11 
1878 
5 
7 
10 
9 
1879 
16 
6 
11 
" 
1880 
10 
15 
12 
12 
1881 
12 
11 
7 
12 
1882 
14 
9 
7 
15 
1883 
8 
20 
7 
10 
1884 
12 
9 
8 
7 
1885 
14 
9 
4 
7 
1886 
14 
21 
4 
3 
1887 
16 
16 
5 
4 
1888 
13 
12 
2 
3 
1889 
15 
12 
6 . 
• 1 
17 years 
164 
159 
114 
132 
It is seen that, of the European foals, pure-bred or half-bred, 
there qre 164 cqlts to 159 fjlljes ; whilst, of the Arabs, away from 
