170 BULLETIN 'OF WISCONSIN NATURAL HISTORY SOCIETY. VOL. 3, NO. 4. 
form, environmental hostility (lack of adaptation in the animal), 
or the sum of its contacts with the environmental will be favorable, 
environmental hospitality (adaptation in the animal). The third 
possibility, that the animal will find the sum of its contacts so 
exactly balanced between the two that their effects will be 
neutralized is so remote that its occurence can only be considered 
as an interesting- possibility. There will of course be all grades 
of hospitality and of hostility from the superlative to the least 
possible that will result in the triumph or extinction of the 
animal. 
Should the animal encounter environmental hostility its 
habits or structure or both must become altered (adapted) or the 
form will perish, and its variants will be more liable to persist 
than the parent. Should it encounter environmental hospitality 
it would survive and variations would be more liable to extinction 
than to preservation (see below). 
The environment of any life form is not necessarily the sum 
of all the factors that we can appreciate. There may be many 
things of which we have no consciousness which bear impor- 
tantly on the form ; or things which we can appreciate only by 
an effort, or things which we appreciate but to which we attach 
no value. To take one of the least complex instances, we appre- 
ciate the color of a flower only through an artifically cultivated 
aesthetic sense but that color is often the determinant factor in the 
environment of the flower or the insect _which visits it. The 
possible number of differing sums of contacts is so enormous that 
it is possible and probable that no two groups of animals have 
exactly the same. 
The fact that forms in a condition of seeming - environmental 
hospitality do develop new forms is explainable on the supposi- 
tion that there are unperceived factors in the environment or 
that of those perceived we have given an undue importance 
to one or more and the sum of contacts may have a reversed 
sign from our determined answer. The very fact of environ- 
mental hospitality must in time produce an opposite condition. 
The condition of environmental hostility may result from two 
sources. 
I. From contact with other animals. This may be again 
subdivided into two parts. Active hostility and passive hostility. 
Active hostility of the environment would mean the attacks upon 
the life of the animal by predatory forms ; perhaps also the attacks 
of parasites and even bacterial invasions. So far as the animal is 
preyed upon by other animals it forms an element of hospitality 
