Natural History of the United States. 325 
ing to the classification of Linnzus, is called by him Primates, expressing, 
no doubt, his conviction that these beings, among whieh Man is included, 
j find, there- 
fore, here as everywhere, the same vagueness in the definition of the dif- 
ki ur s i i 
entific meaning, it seems to me most natural, and in accordance with 
the practice of the most successful investigators of the animal kingdom, 
to call orders such divisions as are characterize by different degrees of 
Complication of their structure, within the limits of the classes. As such 
I would consider, for instance, the Actinoids and Halcyonoids in the class 
of Polypi, as circumseribed by Dana; the Hydroids, the Discophore, and 
Holothurize among Echinoderms; the Bryozoa, Brachiopods, Tunicata, 
among Reptiles; the Ichthyoids and the Anoura among Amphibians, 
etc,” * * *& % 
“From the preceding remarks respecting orders it might be inferred 
that I deny all gradation among all other groups, or that I assume that 
orders constitute necessarily one simple series in each class, Far from 
asserting any such thing, I hold on the contrary, that neither is necessa- 
Tily the case, But to explain fully my views upon this point, I must in- 
4. Ce here some other considerations. It will be obvious, from what 
has already been said, (and the further illustration of this subject will 
only go to show to what extent this is true,) that there exists an unques- 
Nouable hierarchy between the different kinds of groups admitted in our 
. Several classes, that orders are subdivisions of the classes, oe: 
s“visions of orders, genera subdivisions of families, and species subdi 
asses, as this must depend upon the manuer in which the type is carried 
A class, again, might contain no orders, if its representatives Lobe 
whted no different degrees characterized by the greater or less comp a 
Hon of their structure; or ijt may contain many, or few, as these grada- 
4/8 are more or less numerous and well marked ; but as the i nora 
tives of any and every class have of necessity a de nite form, each class 
resentatives ma 
bined, if form can be shown to be characteristic of families. 
e 
A genus may be ; ily characterize 
— more satisfactorily cha , 
— fully ascertained, its limits better defined, when we know all its represen- 
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