CHAPTEE III 



THE VARIABILITY OF SPECIES IN A STATE OF NATURE 



Importance of variability — Popular ideas 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 iu 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 

 has 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 the 

 varieties that occur in each species, and in some cases these 



