A System of Logic: Ratiocinative and Inductive, 7th Edition, Vol. II
CHAPTER VIII. _Of Classification by Series.
ยง 1. Natural groups should be arranged in a natural series 284
2. The arrangement should follow the degrees of the main phenomenon 285
3. --which implies the assumption of a type-species 287
4. How the divisions of the series should be determined 288
5. Zoology affords the completest type of scientific classification 289