THE MULTIPLICATION OF ANIMALS AND SEX 61 
36. The number of young.—There is great variation in the 
number of young produced by different species of animals. 
Among the animals we know familiarly, as the mammals, 
which give birth to young alive, and the birds, which lay 
eggs, it is the general rule that but few young are pro- 
duced at a time, and the young are born 2r eggs are laid 
only once or perhaps a few times in a year. The robin lays 
five or six eggs once or twice a year; a cow may produce 
a calf each year. Rabbits and pigeons are more prolific, 
each having several broods a year. But when we observe 
the multiplication of some of the animals whose habits are 
not so familiar to us, we find that the production of so few 
young is the exceptional and not the usual habit. A lob- 
ster lays ten thousand eggs at a time; a queen bee lays 
about five million eggs in her life of four or five years. A 
female white ant, which after it is full grown does nothing 
but lie in a cell and lay eggs, produces eighty thousand 
eggs a day steadily for several months. A large codfish 
was found on dissection to contain about eight million 
eggs. 
If we search for some reason for this great difference in 
fertility among different animals, we may find a promis- 
ing clew by attending to the duration of life of animals, 
and to the amount of care for the young exercised by the 
parents. We find it to be the general rule that animals 
which live many years, and which take care of their young, 
produce but few young; while animals which live but a 
short time, and which do not care for their young, are very 
prolific. The codfish produces its millions of eggs; thou- 
sands are eaten by sculpins and other predatory fishes be- 
fore they are hatched, and other thousands of the defense- 
less young fish are eaten long before attaining maturity. 
Of the great number produced by the parent, a few only 
reach maturity and produce new young. But the eggs of the 
robin are hatched and protected, and the helpless fledglings 
are fed and cared for until able to cope with their natural 
