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Übersetzungsrecht vorbehalten. 
The effect of Altitude upon the Distribution of 
Mexican Amphibians and Reptiles. 
By 
Hans Gadow, F.R. S. 
With 6 figures in the text. 
It is as well to confess at once our ignorance of the detailed 
working of the many factors which are connected with a change 
of altitude. It implies temperature, atmospheric pressure, and 
according to the locality saturation, cloudbelts, wind, radiation and 
insolation. About the effect of varying pressure upon terrestrial 
animals we know next to nothing, whilst we are beginning to 
correlate the influences of some of the other factors, notably tem- 
perature. If therefore we introduce altitude as a factor in distri- 
bution, we draw our eventual conclusions without knowing which of 
the subfactors of altitude are the determining agents. 
Altitude and longitude can compensate each other. As the 
annual mean temperatur decreases 0,5° C with every 100 m 
elevation, and 0,75° C with every degree of latitude, 10 degrees 
of latitude should be compensated by 1500 m elevation. Thanks 
to the continuous and rather steady rise of the great plateau of 
Mexico from North to South, this theoretical compensation works 
remarkably well. 
A striking example are the following data: 
Lat. N. Altitude Mean annual Temp. 
Chihuahua town 28° 38° 1450 m 18,2° C 
Mexico town 19226: DT lyn 15,5° C 
