ECOLOGY AND BIOLOGY 315 
these differently located areas. This correspondence is probably much 
more striking physiologically than in the matters of interrelation of 
species because in some formations certain groups, as, for example, 
antelopes in African steppes, are especially numerous, while in a 
corresponding situation in South America they are very few. 
As has already been suggested, correspondence is not limited to 
the gross characters of extensive formations, but is equally true of 
the more local communities. In matters of correspondence of species 
there are often striking correspondences within the groups of formation 
indicated above. For example, there is a striking correspondence in 
behavior between the meerkats of the steppes of East Africa (3) and 
the prairie dogs of our own steppe, both being grasslands but differ- 
ing in climate. Considering a local formation, as that of the sandy 
beaches of the sea and very large lakes, we note that along the New 
England coast and around the shores of Lake Michigan the moist, 
sandy beaches are inhabited by the larvae of the beach tiger-beetle 
(Cicindela hirticollis) (Fig. 134, p.179). Along the Gulf Coast at Galves- 
ton, Texas, we find the larvae of C. saulcyi inhabiting almost identical 
situations, holes of about the same depth, etc., while Dr. Horn (203) 
describes a different larva in like situations and with like habits on the 
coast of India. 
Still, with all that has been said, matters of agreement of different 
animal communities in different parts of the world are largely theoretical, 
and while apparently logically well grounded, the general statement 
must be treated with due caution and subjected to experimental test 
as soon as possible. Such testing will involve careful experimental 
study of the communities of two like environments under rigidly con- 
trolled and carefully measured conditions. 
VI. RELATIONS OF ECOLOGY TO OTHER BIOLOGICAL SUBJECTS 
The environmental processes which we are discussing are those in 
which organisms have existed since their origin on earth. The stresses 
and strains to which organisms have been subjected have been in the 
same direction for long periods.’ Now that we have learned much 
concerning organic response to environment, such as_ physiological 
response, behavior response, and structural response, we note at once 
that processes of adjustment and equilibration of living substance may 
bear important relations, on the one hand to environmental processes, 
and on the other to the physiological aspect of biological phenomena. 
