REACTIONS OF ANIMALS. 1 13 



of the breeding period. However there is no good evidence that 

 total temperature above an arbitrary minimum is more significant 

 than is total pressure, total sunshine, total wind movement, or 

 (Walker, '03) total humidity. All must be considered together. 

 Temperature control has "worked" in the mapping of distribu- 

 tion just as any theory whatsoever will work for some species 

 be it concerned with a wandering pole or an Atlantis. The 

 facts and causes of distribution are much more complex than 

 the temperature control assumes. While all facts of distribution 

 are worthy of explanation, the biological processes concerned 

 are of vast importance for they include the most complex 

 problems of biochemistry and life phenomena. The increase 

 in irritability shown by the animals studied, the remarkable 

 water-regulating power of the meal worms, brought out by 

 Berger ('07), the quick regulatory changes of the mammals, 

 and other responses to the physical environment (including the 

 surrounding medium) open many new problems to the biochemist. 

 Our explanation of the phenomena concerned must accord with 

 the facts of relations in nature as well as with the results of the 

 laboratory experiments. Experimental ecological investigations 

 give promise of contributing as much toward the solution of 

 some of the broader biological problems as will the investigation 

 of subjects in fields where speculation has added interest and 

 concentrated attention in years past, and, so far, given us a 

 total progress of questionable significance. 



SUMMARY. 



1. The animals studied react to evaporation whether it is 

 produced by movement, dryness, or heat (p. 105). 



2. The sign and degree of reaction are in accord with the com- 

 parative rates of evaporation in the experiments and in the 

 habitats from which the animals were collected (p. 105). 



3. The animals of a habitat are in general agreement in the 

 matter of sign and degree of reaction ; the minor differences which 

 occur are related to vertical conditions, position of maximum 

 abundance in succession, and kind of integument (pp. 97 and 

 1 06). 



4. Short exposure to high evaporation increases sensibility to 

 evaporation (pp. 87, 90, 91, 95, and 97 (charts)). 



