Chap. XIII. 
CLASSIFICATION. 
417 
birds and reptiles^ as an approach in structure in any one 
internal and important organ. 
The importance, for classification, of trifling characters, 
mainly depends on their being correlated with several 
other characters of more or less importance. The value 
indeed of an aggregate of characters is very evident in 
natural history. Hence, as has often been remarked, a 
species may depart from its allies in several characters, 
both of high physiological importance and of almost 
universal prevalence, and yet leave us in no doubt where 
it should be ranked. Hence, also, it has been found, 
that a classification founded on any single character, 
however important that may be, has always failed; for 
no part of the organisation is universally constant. The 
importance of an aggregate of characters, even when 
none are important, alone explains, I think, that saying 
of Linn80us, that the characters do not give the genus, 
but the genus gives the characters; for this saying 
seems founded on an appreciation of many trifling points 
of resemblance, too slight to be defined. Certain plants, 
belonging to the Malpighiaceae, bear perfect and de¬ 
graded flowers; in the latter, as A. de Jussieu has 
remarked, the greater number of the characters proper 
to the species, to the genus, to the family, to the class, 
disappear, and thus laugh at our classification.” But 
when Aspicarpa produced in France, during several 
years, only degraded flowers, departing so wonderfully 
in a number of the most important points of structure 
from the proper type of the order, yet M. Eichard 
sagaciously saw, as Jussieu observes, that this genus 
should still be retained amongst the Malpighiacese. 
This case seems to me well to illustrate the spirit with 
which our classifications are sometimes necessarily 
founded. 
Practically when naturalists are at work, they do 
T 3 
