THE NATURE OF SPECIES
closing a discussion at the Entomological Society on “What is a Species?” he remarked[1] that he had never conceived of the origin of a species from one ancestral pair, but always from the change of masses rather than of individuals. He added that it was “the splitting of the single community into separate subcommunities which was the foundation of the process.”
These subcommunities were the kinds of groups for which, in 1896, I suggested the term circulus. In a catalogue of the Jurassic Bryozoa, or “moss-animals,” in the British Museum I pointed out that the term species is inappropriate to these groups, because they are not separated by definite boundaries and were not developed by continued divergence into isolated assemblages. The term circulus was suggested from the analogy between these groups and the knots of people who collected around the speakers in the Roman Forum. Each knot would be crowded near the centre and looser on the margin, whence people would frequently pass to an adjacent circulus.
The term circulus was also used in 1900 in a work[2] describing a large collection of fossil corals from the Jurassic deposits of Cutch, in western India. Most of the corals came from one reef, which was especially rich in the simple coral Montlivaltia, of which there were more than 2,000 specimens. Each circulus of these Indian Montlivaltia shows variations as great as those representing species among the corresponding European corals. One of the flat corals, named M. frustriformis because it is shaped like the frustrum of a cone, has fifteen European analogues; a taller hornshaped form, M. cornutiformis, corresponds to twenty European species, and M. kachensis to eleven. In the EuropeanTemplate:Smalrefs
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