218 READINGS IN EVOLUTION, GENETICS, AND EUGENICS 
disturbing the balance of nature, careless of results and ruthless of 
beauty, for not admitting that if we would master Nature we must 
first understand her. How much has Australia had to pay for the 
introduction of rabbits in 1860, or America for sparrows? Sometimes 
the introduction has been unconscious, and man has only to blame 
himself for letting the intruder take hold, as in the case of the Phyl- 
loxera in France, or of the Colorado Beetle in Ireland. ‘Ignorance 
of nature,” Mr. A. H. S. Lucas says, “is costly. By disturbing the 
balance of nature, man has introduced foes into his own household.” 
Speaking of Australia, he says: ‘“‘How much is needed for the eradi- 
cation of Bathurst Burr, Prickly Pear, Water-hyacinth, Bramble and 
Sweetbriar, Codlin Moth, Waxy Scale, Pear Slug, and Red Spider. 
owing to carelessness or lack of knowledge in early days?” 
An obvious moral is that we should be careful in our introduc- 
tions of new organisms—man included—into new surroundings. The 
primary consequences may be predictable, but the secondary and the 
tertiary consequences—who is sufficient for these things? We have 
records of the unconscious introduction of rats into Jamaica, where 
they became a pest. To destroy them mongooses were imported, and 
the rats were soon checked. But the mongooses, having finished the 
rats, began to eat up the poultry and young birds of various kinds. 
As this went on the injurious insects and ticks, that the birds used to 
eat, began to gain the ascendant. A recent report—which requires 
confirmation—says that the increase of ticks is making life a burden 
to the mongooses. Thus a balance will be again arrived at. There 
is no doubt of that, but how much is often unnecessarily lost by the 
way! 
