THE NATURE OF SPECIES
used later (de Vries, 1901) in a nearly opposite sense—that is, to denote sudden variations, or sports.
Herbert Spencer remarked: “Those who reject the theory of evolution as not adequately supported by the facts accept instead a theory which is supported by no facts at all.” The development of specific differences—differences marking species—by gradual change from generation to generation has been well established by collecting fossils from successive layers in a series of deposits and comparing each fossil with its predecessors and successors.
_p117_sea_urchins_in_English_Chalk.png)
Fig. 2.—Sea-urchins formed in the English Chalk.
The sea-urchins in the English Chalk that belong to the extinct genus Micraster (Fig. 1) provide a convenient illustration of the evidence thus obtained as to the actuality and nature of evolution. This sea-urchin is a common and well-preserved fossil, and it shows variations that might be regarded as distinctive of two or more species. The late Dr. A. W. Rowe, of Margate,[1] collected 2,000 specimens of Micraster and carefully recorded for each specimen its level in the Chalk. They show gradual variations (Fig. 2) as they are followed upward through the Chalk. They are of four chief shapes, all of which have come from the earlier
- ↑ Quart. Jour. Geol. Soc., Vol. 55, 1899, pp. 494–547, pls. 35–9.
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