150 ECOLOGY AND LIFE HISTORY OF THE COMMON FROG 



and keep them going for months, and repeat them for years before we 

 could hope to investigate the factors with the same detail as was done 

 in the work described in this chapter by direct analysis of the field data. 



It is, of course, quite illogical to expect a biological situation to be 

 simple, for almost all that have been thoroughly investigated have 

 been found to be very comphcated. This one looks as if it is not an 

 exception to this rule, and anyone contemplating setting up simple 

 experiments of the "frog-in-bottle, one-factor-at-a-time" type should 

 reflect on the following comments by Fisher (1935) — 



"We have usually no knowledge that any one factor will exert its 

 effects independently of all others that can be varied, or that its effects 

 are particularly simply related to variations in these other factors. On 

 the contrary, if single factors are chosen for investigation, it is not 

 because we anticipate that the laws of nature can be expressed with any 

 particular simphcity in terms of these variables, but because they are 

 variables which can be controlled or measured with comparative ease. 

 If the investigator, in these circumstances, confines his attention to any 

 single factor, we may infer either that he is the unfortunate victim of 

 a doctrinaire theory as to how experimentation should proceed, or 

 that the time, material, or equipment at his disposal are too hmited to 

 allow him to give attention to more than one narrow aspect of his 

 problem." 



It is, however, not impossible that, having outlined the main factors 

 operating in the field, and having a hypothesis that seems to fit the 

 facts, laboratory experiments in conformity with the field observations 

 could be useful. It should be easy now to detect irrelevancies, for if 

 the laboratory experiments do not fit the known facts, however 

 interesting they may be in themselves, they would not be relevant. 



It would be quite wrong to conclude this chapter leaving the reader 

 with the impression that the algal hypothesis has been universally 

 accepted. In fact, it is probably true to say that the general attitude 

 has been one of polite incredulity. In reflecting on possible reasons for 

 this, I came across the following remarks by Fisher (1956, p. 40). He 

 was discussing the resistance shown by the normal mind to accepting 

 a story intrinsically too improbable, and listed four common 

 reactions — 

 '\a) The whole thing is a fabrication. 



{b) There is no sufficient reason to tloink that the facts were observed 

 and put on record accurately. 



