23 o JOTTINGS ABOUT BIRDS. 



that I believe Dr. Wallace has generalized too 

 widely ; therefore with that part of Mr. Allen's 

 criticism I have nothing to do ; but I would agam 

 strive to impress upon Mr. Allen and other natur- 

 alists the importance — the vast importance — of com- 

 munit}/ of origin, m explaining many of the difficulties 

 with which the nest-building economy of birds is 

 surrounded. To explain many present anomalies 

 in nidiiication we must look to a remote past, as I 

 suggested in my essay — to the ancient history of 

 dominant forms which in their long descent have 

 undergone many vicissitudes (including the segre- 

 gation of representative forms and species), and been 

 compelled to change their habits, or alter the style of 

 their architecture, and in some cases have retained a 

 mode of nest-building which is now not apparently 

 in harmony with their modified structure or plumage. 

 Further, Mr. Allen must always bear in mind that 

 it is the rule to find certain types of nests peculiar 

 to certain groups or species, such being handed 

 down from a common ancestor, which we can have 

 no doubt were of vital importance to that ancestral 

 form, and harmonized with the conditions of its 

 existence. It is therefore only reasonable to expect 

 to find anomalies amongst many species — to find 

 exceptions to certain broad rules which are readily 



