VOYAGE FROM NEW YORK TO RIO DE JANEIRO. 21 
nature ? I answer, Yes. The standard is to be found in 
the changes animals undergo from their first formation 
in the ea'g to their adult condition. 
oo 
" It would be impossible for me here and now to give 
you the details of this method of investigation, but I can 
tell you enough to illustrate my statement. Take a homely 
and very familiar example, that of the branch of Articulates. 
Naturalists divide this branch into three classes, Insects, 
Crustacea, and Worms ; and most of them tell you that Worms 
are lowest, Crustacea next in rank, and that Insects stand 
highest, while others have placed the Crustacea at the head 
of the group. We may well ask why. Why does an insect 
stand above a crustacean, or, vice versa, why is a grass- 
hopper or a butterfly structurally superior to a lobster or a 
shrimp ? And indeed there must be a difference in opinion 
as to the respective standing of these groups so long as 
their classification is allowed to remain a purely arbitrary 
one, based only upon interpretation of anatomical details. 
One man thinks the structural features of Insects superior, 
and places them highest ; another thinks the structural 
features of the Crustacea highest, and places them at the 
head. In either case it is only a question of individual 
appreciation of the facts. But when we study the gradual 
development of the insect, and find that in its earliest stages 
it is worm-like, in its second, or chrysalis stage, it is crusta- 
cean-like, and only in its final completion it assumes the 
character of a perfect insect, we have a simple natural scale 
by which to estimate the comparative rank of these animals. 
Since we cannot suppose that there is a retrograde move- 
ment in the development of any animal, we must believe 
that the insect stands highest, and our classification in this 
instance is dictated by Nature herself. This is one of the 
