3fiO Molls' System of Crystallography 
unite more closely with each other than with the restj according 
to the measure of their similarity ; and therefore a series of 
single species would result, having an extent equal to that of 
the mineral kingdom. The conception of the mineral kingdom 
would thus be changed into that of a series of single species. 
38. Higher and lower degrees of similarity . — Neither the 
one supposition (37.), nor the other (38.), is found to hold in 
nature. The degrees of similarity between the different species 
are neither altogether equal nor altogether unequal. It is there- 
fore true, that both higher and lower degrees of this similarity 
are found to exist ; and though not necessary in this place, it 
would be proper to enter upon an analysis of them, in order to 
produce examples of this fact, if the annexed mineralogical sy- 
stem did not serve instead of all examples. 
39. No series of species in mineralogy . — To convince him^lf 
of the truth that higher and lower degrees of mineralogical si- 
milarity have a real existence, and hence that no single series of 
species can possibly be found in the mineral kingdom, — let any 
one make the attempt actually to represent to himself such a se- 
ries. He will soon fall upon species, concerning which doubts 
will arise whether the one or the other, or even a third or 
fourth, ought to come next in order; and at last he will feel 
himself compelled to assign one and the same place to two, 
three, or even more. Instead of single species, therefore, 
groups of species would result ; from which it follows, that in 
this department, as well as in the animal and vegetable king- 
doms, no regular gradation, or series of single species^ is any 
where to be met with. 
.40. Germs . — A collection of species connected by the highest.^ 
and, at the same time, equal degrees of natural historical simila- 
rity, is named a genus 
41. The idea of genus is the same as in zoology and botany. 
— This idea of genus is exactly the same as that wliich zoology 
and botany employ, in their natural systems. According to 
this idea, the wolf, dog, fox, — the lion, tiger, cat, — unite into 
genera; and the application of this principle is the basis on 
which the distribution into genera rests, throughout the whole 
of nature, whenever the intention is to found a natural system. 
