ZOOLOGY. 227 
ositions are: “1st, Morphology is the only safe guide to the classifi- 
cation of organized beings, teleological or physiological adaptation 
being the most unsafe guide, and conducing to the most unnatural 
approximations; 2d, The affinities of such organisms are only 
determinable by the sum of their agreements in morphological 
characteristics, and not by the modifications of any single organ.” 
The first proposition we think so self-evident, that it is surpris- 
ing that there are naturalists who, in practice at least, do not con- 
sent to it. Morphology is simply the determination of what the 
elements of an organism are; a question which obviously lies at the 
root of things, and demands attention before the question of the 
uses of said parts can be considered.* , 
The discussion of the second proposition involves the main ques- 
tion. I conceive it to be a very good expression of the views of 
many naturalists, yet, in my own, it does not go far enough; nor is 
the second clause, that “affinities are determinable” “not by the 
modifications of any single organ,” one with which I can_ agree. 
The same objection therefore applies to the corollary following, that 
“the adoption of such principles compels us to reject such systems 
as are based solely on modifications of the brain, those of the 
placenta, and those of the organs of progression,” etc. In other 
words, agreeing with the first part of Prop. 2, that “ affinities” 
“are only determinable by the sum of their agreements in morpho- 
logical characteristics,” we do not regard the remainder of the 
proposition and its corollary as necessary consequences of it. 
If we analyze the “sum of the agreements” of given groups, 
we cannot affirm’ that all of those separate characters which con- 
stitute that sum have been always, in past time, coéxistent. In 
fact, we know that they have not been so, and that the differences 
of groups consist in the abstraction of single characters from, or 
addition of single characters to, this “sum.” Hence the history 
of this “sum” is the history of the single characters which 
compose it, and each one of them has a special value of its own, 
which cannot be sunk in a state of association. If this be 
true, systematic zodlogy stands upon what some naturalists are 
pleased to call a purely “technical” basis, as opposed to what 
they term a“natural” one. And this is distinctly our position. 
_ Every structural feature possesses some systematic value, and when 
our knowledge extends over a greater number of forms than the 
* See Proceedings Academy of Natural Science, Phila., 1863, p. 50; Natural 
History Review, 1865, p. 98, etc., where this view is expressed. 
