4 
light we may perhaps see the meaning of a sentence from a work 
which will be repeatedly referred to in this narrative, viz. :— 
‘ This body in which we journey across the isthmus between the 
two oceans is not a private carriage, but an omnibus.”’—(The 
Guardian Angel.) 
This union of different elements is well expressed by 
Matthew Arnold in the following lines :— 
“ Born into life !—man grows 
Forth from his parents’ stem, 
And blends their bloods, as those 
Of theirs are blent in them— 
So each new man strikes root into a far fore time.” 
—(.Empedocles on Etna.) 
In the second place, it should be observed that this 
“ individuality of the individual ” may co-exist with the 
most absolute fixity of the type. “ Nature,” says Milne 
Edwards, “is prodigal in variety but niggard in innovation.” 
There is only one way of dealing with this particular 
kind of variation in order to produce a transmutation of 
species, namely, that those variations which are similar to 
one another should be “selected,” i.e., that they should be 
isolated for breeding purposes from the other variants 
which have not their peculiar characteristics. “ Man,” says 
Mr. Belt, “ isolates varieties and breeds from them ; and 
continuing to separate those that vary in the direction he 
wishes to follow, a very great difference is in a compara 
tively short time produced.”* 
But in order that this process should be successful, the 
isolation must be strictly and persistently carried out for 
many generations until the variation is fixed in the race. 
Mr. Darwin assures us that— 
“ A species may be highly variable ; but distinct races will not be 
formed, if, from any cause, selection be not applied. The carp is 
highly variable : but it would be extremely difficult to select slight 
The Naturalist in Nicaragua, p. 207.