On the Variation of Species, with Especial Reference to the Insecta Followed by an Inquiry into the Nature of Genera

CHAPTER III.

Chapter 240 wordsPublic domain

Causes of Variation § 1. Climatal causes generally (whether dependent upon latitude or upon altitude) § 2. Temporary heat or cold, of an unusual degree § 3. Nature of the country, and of the soil § 4. Isolation; and exposure to a stormy atmosphere