458 R. T. YOUNG 



performed upon caged animals, and it is quite possible that 

 confinement materially alters their senses. The space factor 

 also enters into experiments with caged animals, by limiting 

 the distance between them and their prey. I shall refer at 

 greater length to these objections later on. • 



In addition to the experiments cited by Beddard (I.e.) and Poul- 

 ton ('90), the most important work I know of is that of Finn 

 ('98), Judd ('99), Pritchett ('03), and Reighard ('09), all deal- 

 ing chiefly with warning color. Taken as a whole, these ex- 

 periments are inconclusive, some of them supporting, others 

 refuting, the theory. Their general tendency, however, has 

 been to cast grave doubts upon it. There are a few isolated 

 experiments on protective coloration proper, but they are too 

 few to carry much weight and their results are also contradictory. 



Among the criticisms of this theory is the objection that such 

 coloration is not really protective, and that animals possess- 

 ing it seek refuge in other ways, as in flight and hiding. Thus 

 Werner ('07), sarcastically refers to a certain supporter of this 

 theory as a 'Sonntagsjager,' and cites evidence supposedly pro v • 

 ing the inefficiency of color in protecting its possessors from their 

 enemies. 



To put the theory to an experimental test, I have carried 

 out a series of 144 experiments during the past six years, using 

 for the purpose crows, hawks, owls, domestic chickens, prairie 

 chickens, grackles, kingbirds, and martins as preyers, and several 

 kinds of mammals and insects as prey. 



The photographs illustrating this article were taken on Cramer 

 ischromatic plates through a ray filter, i- ' and printed on 'glossy 

 Cyko' paper manufactured by the Ansco Company of Bingham- 

 ton, New York. 



Considerable difficulty attends a representation of color con- 

 trasts by photography, as the effect upon the photographic 

 plate is not necessarily the same as upon the human retina. 

 Very different effects may be obtained by manipulating either 

 the exposure or the development of the plate, or both. I have 



^ Ingento,' Series B, Burke and James, Chicago, Illinois. 



- Except figures 37, 50, and 52, in making which no filter was used. 



