40 ANIMAL ECOLOGY 



turns to any student well prepared in each line of 

 work. 



Another essential for good field work is a clear 

 understanding of what ecological studies attempt 

 to do. This implies some general conception of 

 what is worth while ecologically ; it assumes a point of 

 view or other criterion which may be applied to 

 test the trueness of one's aim. The ecologist will 

 meet with much more than ecological facts, but it is 

 to these that he should give primary attention. 

 These accessory facts, no matter how interesting in 

 themselves, should not divert him from the main 

 course. The ecologist must select from this mass of 

 experience those facts, inferences, and conclusions 

 which help in the interpretation of the responses of 

 animals to their complete environment. It is thus 

 evident why the ecologist must have a clearly 

 defined aim, with criteria for estimating values, 

 or he will be at the risk of dissipating his energies. 

 This phase of our problem as applied to the studies 

 of a geologist, but applying with equal force to the 

 ecologist, has been concisely expressed by Van 

 Hise (1904, pp. 611-612) as follows : "I have heard a 

 man say : ' I observe the facts as I find them, un- 

 prejudiced by any theory.' I regard this statement 

 as not only condemning the work of the man, but 

 the position is an impossible one. No man has 

 ever stated more than a small part of the facts with 

 reference to any area. The geologist must select 

 the facts which he regards of sufficient note to record 

 and describe. But such selection implies theories of 



