APPENDIX 



The second specimen had mated with a normal 

 cock. In each case the Isabelline birds were very 

 much more docile than the normal forms. For 

 instance, they did not struggle when picked up, as 

 the others would have done, and the third specimen, 

 when brought into our hut, gazed around with 

 curiosity and apparent contentment, and showed 

 not the least resentment at its captivity. A normal 

 bird would have struggled and fought to the last 

 extremity. Each bird was killed with chloroform. 



So carefully did we keep the entire rookery under 

 observation that I do not think it likely there were 

 any more Isabelline forms. Thus we can con- 

 clude 7scPooo roughly represents the proportion of 

 Isabelline forms among the species. 



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