IMMIGRATION OF ANIMALS AND PLANTS. 

ReaD BEFORE THE SCIENTIFIC ASSOCIATION, SEPTEMBER, 1886, 
BY FRED BRENDEL, M.D. 

There is no stability in nature, all thingschange. Individuals change during 
life, species change in time, associations of species change by suppression and 
supplantation, climate changes, and with it the appearance of landscape. Such 
changes are not obvious when we compare only short periods, as single years, 
for they take place slowly step by step; they are conspicuous only when we 
compare longer periods, either from what we know by personal experience or 
what we learn from history. We read in the works of old Greek authors de- 
scriptions of their country, of shady groves full of lively springs, when now 
Greece is an arid country; the woods are gone and the abundance of springs. 
Many plants are mentioned that now-a-days are not found there, and conspicu- 
ous plants are not mentioned that grow there at present, and would not have 
escaped notice had they been there contemporary with those writers. At the 
same time Germany was covered by an uninterrupted forest, and it is quite im- 
probable that the many weeds now found in fields and sunny places, around 
houses and in gardens, have grown there at that time; they must have immi- 
grated after cultivation of the country. 
As already said, changes in the aspect of a country are effected by sup-. 
pression and supplantation, with other words, extinction of constituent parts of 
the whole and substitution of others by immigration, the latter ones being the 
more powerful.in the struggle for existence. 
Before this country was settled by our race, the red man hunted the buffalo 
on the prairie and the bear in the forests. The red man is gone, the but- 
falo is gone, and the black bear; the elk is gone and the beaver; civilization 
pushed them westward with the red man since more than half a century. 
Changes in the animal habitation did not stop since. Forty years ago the bot- 
tom woods swarmed with paroquets, now not a single one is found in Illinois. 
Many birds once abundant are scarce now, when on every tree of this city 
scores of noisy house-sparrows fill the air with their chirping, unknown there 
15 years ago, This impudent intruder chased the blue birds away and somany 
lovely birds. Until now he is only the unwelcome inhabitant of the city, but 
as he is prolific in a high degree, soon there will not be room enough in town, 
and he will spread over the whole country, as the rats did and the mice. 
When a foreign animal or plant becomes perfectly at home in a country we 
call it naturalized, when naturalization is not perfect the new comer is called 
adventive; then it is uncertain whether the settlement will be permanent or 
not. Sometimes, by chance, single individuals appear, but do not settle at all. 
I recollect such stragglers that were captured in our vicinity, —one bird from 
the northwest, the evening grosbeak (Hesperiphona vespertina), and one but- | 
terfly from the southwest (Terias Mexicana). I have never seen a second one. 
Some insects appear in single years in immense numbers, doing much dam- 
age in certain districts. This is not by migration, for the same kind exist in 
the same locality before and after, only in a smaller number. A beetle of the 
