Ill 
VARIABILITY OF SrECIES IN A STATE OF NATURE 81 
naturalists of the old school, and all mere collectors, were 
interested in species in proportion to their rarity, and would 
often have in their collections a larger number of specimens 
of a rare species than of a species that was very common. 
Now as these rare species do really vary much less than the 
common species, and in many cases hardly vary at all, it was 
very natural that a belief in the fixity of species should 
prevail. It is not, however, as we shall see presently, the 
rare, but the common and widespread species which become 
the parents of new forms, and thus the non-variability of any 
number of rare or local species oilers no difficulty whatever in 
the way of the theory of evolution. 
Concluding Remarks. 
AVe have now shown in some detail, at the risk of being 
tedious, that individual variability is a general character of all 
common and widespread species of animals or plants; and, 
further, that this variability extends, so far as we know, to 
every part and organ, whether external or internal, as well as 
to every mental faculty. Yet more important is the fact that 
each part or organ varies to a considerable extent inde¬ 
pendently of other parts. Again, we have shown, by abundant 
evidence, that the variation that occurs is very large in 
amount—usually reaching 10 or 20, and sometimes even 25 
per cent of the average size of the varying part; while 
not one or two only, but from 5 to 10 per cent of the speci¬ 
mens examined exhibit nearly as large an amount of variation. 
These facts have been brought clearly before the reader by 
means of numerous diagrams, drawn to scale and exhibiting 
the actual variations in inches, so that there can be no pos¬ 
sibility of denying either their generality or their amount. 
The importance of this full exposition of the subject will be 
seen in future chapters, when we shall frequently have to 
refer to the facts here set forth, especially when we deal with 
the various theories of recent Avriters and the criticisms that 
have been made of the Darwinian theory. 
A full exposition of the facts of variation among wild 
animals and plants is the more necessary, because compara¬ 
tively few of them were published in Mr. Darwin’s works, 
while the more important have only been made known since 
G 
