382 EVOLUTION, GENETICS, AND EUGENICS 



V 



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 i860, 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 

 wayl 



