Quinarianism gets its name from the emphasis on the number five: it proposed that all taxa are divisible into five subgroups, and if only four subgroups are known, quinarians believed that a missing subgroup remained to be found.
Presumably this arose as a chance observation of some accidental analogies between different groups, but it was erected into a guiding principle by the quinarians. It became increasingly elaborate, proposing that each group of five classes could be arranged in a circle, with those closer together having greater affinities. Typically they were depicted with relatively advanced groups at the top, and degenerate forms towards the bottom. Each circle could touch or overlap with adjacent circles (a phenomenon called 'osculation').
Another aspect of the system was the identification of analogies across groups:
Quinarianism was not widely popular outside the United Kingdom; it had become more or less unfashionable by the 1840s, during which time more complex "maps" were made by Hugh Edwin Strickland and Alfred Russell Wallace. Strickland and others specifically rejected the concept of "analogy". These systems were eventually discarded in favour of principles of classification based on evolutionary relationship.
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Last updated on Friday August 08, 2008 at 02:44:28 PDT (GMT -0700)
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