178 BULLETIN OF WISCONSIN NATURAL HISTORY SOCIETY. VOL. 3, NO. 4. 
that a species, genus, family, etc., has a definite span of life 
comparable to that of an individual ; that it has its inception, 
period of growth, period of decay and death and that this is de- 
termined by some force inherent in the group itself. If the fact 
is kept in mind that the genus and higher are but groups of con- 
current characters and have no individual life this idea loses 
much of its force. If we consider the lowest group, the species, 
where the idea would have its strongest support it can be shown 
to be at least gratuitous. The birth of a species is the growth 
to recognizable quantity of the number of individuals responding 
to a certain definite group of contacts ; having attained environ- 
mental hospitality the species increases in number until it reaches 
the limit of hospitality in the environment and is checked by the 
concomitant hostile contacts. As the hospitality reaches its limit 
and hostility intervenes some certain variables will become im- 
portant as they have the ability to use the same environment as 
the parent, plus or minus one ; but this ability to use the sligthly 
variant environment determines its success and it becomes an 
important .and fatal element of hostility to the parent as it re- 
sponds so nearly to the same group of contacts as the parent 
which must wane as the variable grows. Of course a slight 
change in the environment might produce the same effect before 
the animal had matured its own hostility. 
The theory of continuously improved structure is deceptive in 
statement, the idea is strictly anthropomorphic. There is no 
theory of continuously better adaptation for the conditions toward 
which adaptations tend are continuously changing and the varia- 
tion is as liable to reverse the previous direction of change as to 
continue it. If anything, it should be called the theory of more 
and more perfect differentiation; the response to the smaller and 
smaller elements in the sum of contacts. 
The idea of improvement in the fancied approach to the mam- 
malian and human type may therefore be dismissed. The true 
statement is that in time forms have become increasingly com- 
plex. This increase in complexity is due to the response to in- 
creasingly small (in quantity) differences in the sum of contacts 
of related species or varieties ; for instance, the general differ- 
ence between two groups may be as the difference between 4 and 
5 but between two species of one group it may be as the difference 
between 4.9764 and 4.9765. A difference in the 10000 place may 
mean a quantitative difference so great as determine the hostility 
or the hospitality of the environment. A reindeer has four legfs 
but it is almost entirely dependent on reindeer moss for food. 
