i88 3 .] 
Rational Marriage-Law. 
58i 
action of two individuals is required. Where the sexes are 
distinct, we find manifold provision to ensure the mating of 
males and females which are not respectively born of the 
same parents. Thus in the case of the solitary wasps and 
bees, though in some species the mother deposits her eggs 
in a single excavation in the trunk of a tree, or in a post, 
yet the larva which first reaches maturity flies away in 
search of a mate, as do the others in succession, and it is 
thus rendered exceedingly improbable that any two of them 
should meet again. 
Since experiments have been made in India on the pro- 
duction of silk from certain so-called “ wild ” moths, of the 
genera Bombyx, Attacus , &c., it has been found that the 
males, on issuing from the cocoon, do not attempt to have 
intercourse with the young females, their sisters, but fly 
away. In their place stranger males arrive, and immediately 
set about copulation. 
Another important agency to prevent in-breeding is that 
young animals, as they approach maturity, become less and 
less gregarious. Sometimes they separate spontaneously, 
and in other cases they are driven away by their parents, 
dispersion being thus effected. 
Many kinds of caterpillars, even though up to that point 
they may have lived in large societies, all the descendants 
of one mother, yet when about to assume the pupa state 
set out on their travels, and often stray to a considerable 
distance from the plant upon which they feed. In many 
kinds of birds the two sexes seem during the winter to form 
distinct societies, and only seek each other up in the spring. 
In some migratory species the males and the females often 
arrive in separate flocks, at an interval of a few days — a 
habit which must render the pairing of brothers and sisters 
exceedingly unlikely. 
These few instances, which might be greatly extended 
from faCts already on record, and still more so from a special 
and closer study of the subject, prove that there exists a 
Marriage-Law throughout the organic world, the objeCt of 
Nature being evidently that every female shall be fecundated, 
if at all, by a male of different blood. Consanguinity is the 
only bar recognised, and the one objeCt to be avoided is 
degeneration. 
From the lower animals we pass to man. Here it is 
proved beyond doubt that consanguineous marriages lead to 
a deteriorated offspring. Among the pernicious results deaf- 
mutism is one of the most common. Recent investigations 
show that in Berlin this affection is rare among adherents 
