500 Allen, The Concealing Coloration Question. [oct. 



observations. He states, without qualification, that such and such 

 an animal is advertisingly colored. Well, perhaps it is, but the 

 mere statement does not prove it. I have tried to show in an 

 earlier part of this paper why we should be slow to accept all his 

 statements without question, while giving him credit for wide 

 experience and honesty of intention. Let us consider his methods 

 of study as compared with Thayer's, and determine, if we can, 

 which are the more trustworthy. Roosevelt's methods are those 

 of pure observation in the field, with the animals under natural 

 conditions: Thayer uses experiment in addition to observation. 

 Now I should be the last man to depreciate observation. It is 

 the particular form of scientific work that most appeals to my 

 personal tastes. Laboratory methods in the study of living ani- 

 mals have their uses, however, and are more and more being used. 

 By these methods only can we control conditions, so as to isolate 

 the particular class of facts that we are investigating. Rightly 

 safeguarded, this mode of research is invaluable. And it seems to 

 me that in investigating concealing coloration we cannot get along 

 without it, for the simple reason that it is impossible to observe 

 anything that is concealed from the eye. When an animal is 

 showing to the best advantage the concealing power of its colora- 

 tion, that is the very time when we do not see it. I suppose, 

 therefore, that the times when the observer can see this principle 

 in operation in the field are so infrequent, comparatively speaking, 

 that one may get a wholly wrong impression as to the relative 

 conspicuousness of an animal from mere observation and memory. 

 The number of times when a bird, for instance, just fails to elude 

 us ought to be multiplied by a substantial figure in order to include 

 all those individuals which actually do elude us. Of course, 

 no bird of any color can blend into its background all the time. 

 All birds of potentially concealing coloration must sometimes, 

 often in fact, be seen against backgrounds that reveal them. 

 And it is on just these occasions that the observer is most likely 

 to see them. Moreover, the birds that are seen against a back- 

 ground that they match, detected by following their flight per- 

 haps, hold the eye as long as the observer watches them and so 

 tend to be regarded as conspicuous. In other words, as Thayer 

 has pointed out, it is the animals that are seen that make their 



