the natural Distribution of Insects and Fungi. 55 
other case there is only an hiatus or chasm, which the discove- 
ries of a future day may fully occupy. Speaking therefore 
theoretically, it may be affirmed that a saltus never did exist in 
nature; and it also may be argued, with great appearance of 
truth, that if the iatus are real which so commonly occur in 
nature, they did not always exist; or, in short, as M. Fries 
expresses himself, ** Omnis sectio naturalis circulum per se clausum 
exhibet.” 
Now this definition of a natural group could never have been 
given by any person who was not aware of the distinction to be 
made between affinity and analogy. But whenever two parallel 
series of objects linked by affinity are drawn up in array, the 
connexion of their extremes, that is, the formation of the circle, 
becomes in that very moment, so far as I have observed, more 
or less conspicuous. 
It follows, moreover, from admitting the existence of analo- 
gical relations, or, in other words, from laying down the paral- 
lelism of groups in different series of affinity, that the number 
of groups in these series must be the same. For were it other- 
wise, as for instance, supposing three groups to exist in one 
complete series, and four in another, it is clear that the paralle- 
lism could not exist. But if this parallelism be real, which has 
been, as shown above, asserted independently of each other by 
several naturalists acting in different branches of natural his- 
tory, then the number of groups of the next lower order com- 
posing a group of a given degree must be determinate. And if, 
moreover, we accord to our author the accuracy of the following 
rule, namely, * Nunquam negligendum, unumquodque regnum, 
ordinem, genus, &c. in systemate ut individuum esse sumen- 
dum ;"—in other words, that class bears the same relation to 
class which order does to order, and genus to genus; then the 
number of groups composing any group of the next higher 
degree 
