V i°S 9 f] Correspondence. 373 



CORRESPONDENCE. 



[Correspondents are requested to write briefly and to the point. No attention will 

 be paid to anonymous communications.} 



The Evolution of the Colors of North American Land Birds. — A Reply 



to Criticism. 



To the Editors of 'The Auk' : — 



Dear Sirs: In 'The Auk' for April Mr. Allen takes occasion to 

 review my recent paper, finding therein little to commend and much to 

 condemn. Were his remarks mere statements of personal opinion I should 

 not venture to question them, but as he has mentioned a number of pas- 

 sages confirming his opinions, it seems to me that they are worthy of a 

 somewhat fuller discussion. It is generally held a just criterion of 

 criticism to judge a writer by what he has professed to do rather than to 

 blame him for not accomplishing what was not attempted, but this rule 

 Mr. Allen seems to have disregarded. He does me the justice of quoting 

 fully from the preface the intention of the paper, viz., to put forth a 

 provisional explanation of the markings of birds suppported by a greater 

 or less number of facts, with the hope of awakening interest ami stimu- 

 lating research in a new field, but in the rest of his review treats this 

 statement of my intentions as if it had no reference to the work in hand. [1] 

 He seems to have little respect for speculative science, ami condemns the 

 philosophizing of Poulton, Romanes, and Weismann. It appears remark- 

 able indeed that any scientist since the time of Darwin should be too 

 narrow to see the value of such work. For example, Mr. Allen is a firm 

 believer in the inheritance of acquired characters, and can he for a moment 

 deny that the intense discussion of this subject incited by the researches 

 and speculations of Weismann has given the world a far deeper and 

 broader insight into this most intricate of questions? [2] There can be 

 no doubt that the speculative method is open to great abuse when recklessly 

 pushed in advance of empirical observation, but when coupled with this 

 it becomes all important in the advance of real knowledge. Mr. Allen 

 would have us progress only along such lines as we can absolutely estab- 

 lish for all time, but this is clearly impossible. Science like all other 

 knowledge is a process of growth in which there is a continual selection 

 of truth and an elimination of error. Let us by all means have an abun- 

 dance of material to select from. Look at almost any scientific work of 

 fifty years ago, and unless it treat of mathematics it will be found value- 

 less, in large measure, at the present time, although its place may have 

 been an important one as a stepping stone to something better. 



But aside from general considerations, it is of some of his detailed 

 criticisms that I wish to speak. Mr. Allen says without any reservation 

 that my interpretation of the change of color in the young Arizona Hooded 



