MANAOS AND ITS NEIGHBORHOOD. 299 
the dog of pure type the favorite companion of civilized 
man. The question respecting the relation of the human 
races to each other is complicated by the want of precision 
in the definition of species. Naturalists differ greatly in 
their estimation of the characters by which species are to 
be distinguished, and of their natural limitations. I have 
published elsewhere my own views on this subject. I 
believe the boundaries of species to be precise and un- 
varying, based upon a category of characters quite distinct 
from those on which the other groups of the animal king- 
dom, as genera, families, orders, and classes, are founded. 
This category of characters consists chiefly in the relation 
of individuals to one another and to their surroundings, 
and in the relative dimensions and proportions of parts. 
These characters are no less permanent and Constant in 
the different species of the human family than in those 
of any other family in the animal kingdom, and my ob- 
servations upon the cross-breeds in South America have 
convinced me that the varieties arising from contact be- 
tween these human species, or so-called races, differ from 
true species just as cross-breeds among animals differ from 
true species, and that they retain the same liability to 
revert to the original stock as is observed among all so- 
called varieties or breeds." 
Our visit to Mauhes will be the pleasanter and doubtless 
the more successful, because Dr. Epaminondas, who has 
already done so much to facilitate the objects of the ex- 
pedition, takes this opportunity of visiting a region with 
which, as President of the province, he is desirous of be- 
coming acquainted. He is accompanied by our host, Mr. 
Honorio, whose house has been such a pleasant home for 
us during our stay in Manaos, and also by Mr. Michelis, 
