V0l 'i9n VI11 ] Thayer, Concealing Coloration. 463 



The oft-repeated objection that the wearers of these costumes 

 perpetually reveal themselves by motion, and that consequently 

 my tests give a wrong impression, is just what shows lack of 

 taking in what my investigation is. My whole assertion is that 

 the costumes of these creatures are not what reveal them, and the 

 objector's repeated declaration that the real animal moves and 

 shows himself simply backs me up. The use of motionless stuffed 

 skins is the pure method of studying the effect of the patterns 

 apart from that of motion. 



In behalf of those who would like to trust our book, there are a 

 few things that it is best to say about the recent attack on it by 

 Dr. Thomas Barbour and Mr. J. C. Phillips. These men have 

 committed toward us many offenses. They have tried to write 

 down a book which they prove that they have never read with any 

 thoroughness. One example must here suffice. They write that 

 in their judgment a flamingo would look dark against a dawn or 

 evening sky,— saying this with the evident aim of implying that 

 we state the contrary. In our text twice, and five times in the 

 legends over the pictures, we clearly go over this point. Seven 

 times in all. Their article contains four or five other serious 

 misrepresentations of our book, aside from several misstatements 

 about my private history. 



As to Mr. H. C. Tracy's studious and most courteous article on 

 white top marks as directive in flight, it is as obvious to me as 

 to him that whatever constant pattern a creature wears is sure to 

 aid in its recognition, both at rest and in flight. Also, that if he 

 were right that white patterns displayed in flight tend to make 

 the wearer's course more conspicuous to its companions, these 

 patterns might be assumed to owe their existence in corresponding- 

 degree to this use. The trouble is, however, that it seems plain 

 that such is not the case. Flight implies being more or less higher 

 than the ground. In the open, the first bird to take flight is seen 

 by his companions against sky, or at the angle where sky is to be 

 expected, and from this view his whites tend to efface him. Then, 

 when many birds are on wing together in the open, they are on an 

 average moving on a level, i. e., on a tangent to the earth's surface, 1 



i More accurately, a tangent of a sphere larger than the world, and, of course, 

 outside of it. 



