Mutational Mosaic Coat Patterns of the Guinea Pig.
TABLE OF CONTENTS PAGE INTRODUCTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333 The Color Factors of Guinea Pigs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334 A Somatic and Germinal Mosaic (Ccd+Cdcd). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336 Two Intense-dilute Mosaics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342 An Agouti-black Mosaic ( A A +aa) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344 Two Intense-dilute Mosaics ( F f + j ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345 An Intense Brown-pale Brown Mosaic (Pp+pp). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347 DISCUSSIOV.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 348 LITERATURE CITED.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 351
Sewall Wright on Evolution in Mendelian Populations and the “Shifting Balance”
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After the rediscovery of Mendel’s work in 1900, bitter disputes erupted between the first geneticists and the biometricians who studied quantitative traits. How could the discrete genes of the geneticists explain the continuous variation observed by biometricians? And could
The Bearing of Some General Biological Facts on Bud-Variation
I TAKE it no one denies that in the Angiosperms variations may be produced in connection with reproduction by means of buLds and that these variations may be perpetuated by the same m-nethod. Practically, as horticulturists and plant breeders, we care little about the occurrence of bud-variations elsewhere in the organic world. Nevertheless, it may help in the orientation of our ideas if we remember that budding is not a rare or unconventional method of reproduction. In a generalized form, the earliest method, it has persisted througho-ut the plant kingdom front the most primitive to the highest, and most specialized types. Sexual reproduction has not replaced it, but has been added to it. Even in the animal kingdom, though eliminated among the higher forms, it still exists as an occasional alternate method in three fourths of the phyla. Such being the case, it would seem logically to follow that variation must have been within its possibilities. The cause, the frequency, the type, the constancy, the mechanism, of these variations are more debatable, however, and on these questions many biological facts which superficially seem unconnected, have a. direct bearing. In