CHAPTER 111 
THE VARIABILITY OF SPECIES IN A STATE OF NATURE 
Importance of variability — Popular iileas regarding it — Variability of the 
lower animals — The variability of insects — Variation among lizards 
— Variation among birds — Diagrams of bird-variation — Number of 
varying individuals — Variation in the mammalia — Variation in 
internal organs — Variations in the skull — Variations in the habits 
of Animals — The Variability of plants — Species which vary little — 
Concluding remarks. 
The foundation of the Darwinian theory is the variability of 
species, and it is quite useless to attempt even to understand 
that theory, much less to appreciate the completeness of the 
proof of it, unless we first obtain a clear conception of the 
nature and extent of this variability. The most frequent and 
the most misleading of the objections to the efficacy of natural 
selection arise from ignorance of this subject, an ignorance 
shared by many naturalists, for it is only since Mr. Darwin 
lias taught us their importance that varieties have been 
systematically collected and recorded; and even now very 
few collectors or students bestow upon them the attention 
they deserve. By the older naturalists, indeed, varieties — 
especially if numerous, small, and of frequent occurrence — 
were looked upon as an unmitigated nuisance, because they 
rendered it almost impossible to give precise definitions of 
species, then considered the chief end of systematic natural 
history. Hence it was the custom to describe what was 
supposed to be the “ typical form ” of species, and most 
collectors were satisfied if they possessed this typical form 
in their cabinets. Now, however, a collection is valued in 
proportion as it contains illustrative specimens of all tho 
varieties that occur in each species, and in some cases these 
