The course of evolution by differentiation or divergent mutation rather than by selection (1940) (20515488889)

Title: The course of evolution by differentiation or divergent mutation rather than by selection
Identifier: courseofevolutio00will (find matches)
Year: 1940 (1940s)
Authors: Willis, J. C. (John Christopher), 1868-1958
Subjects: Evolution; Natural selection; Variation (Biology)
Publisher: Cambridge (Eng. ) The University press; (New York, Macmillan)
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library



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CH. XI) B. MORPHOLOGICAL 111 equal. The diagram will serve for the growth of the families under differentiation, in which progress is supposed to work downwards from the original species and genus that began the family, A, B, or C, both species and genus of course being the same plant. As the family grows, it will form new species and genera, and all will on the average survive, so that the now existing family is in each case represented by all the dots under A, B, or C Whether the whole family, if seriously old, survive like this, will depend upon Level 1
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C. Cc. Cbb Cb CbChbCc C Fig. 8. Diagrammatic origin of small, medium and large families under differentiation, to show relative rank of genera in each, which goes more or less with the line 1, 2, 3 etc. upon which they happen to stand. what geological or other catastrophes it has met with, and whether any general change may occur in a genus, causing its death, or transforming it, or more probably one of its species, into another genus. The well-known fact that the smell was lost at the same time by all known examples of the common musk, once universal in cottage windows by reason of its sweet scent, shows that though a species may be represented by innumerable individuals, something may happen simultaneously in the internal make-up of all of them. And there is nothing to show that larger mutations than this are not possible. The way in which the successive fossil species of Stratiotes appear in different geological horizons, each specifically different from the preceding one, shows the kind of