Pamphlets on Biology Volume 2966; Kofoid Collection (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1901 Excerpt: ...that these facts lend any support whatever to the genotype theory18 seems to me to rest not only upon the most slipshod reasoning, but upon a complete disregard of simple biological precautions. The chief of the pertinent reasons follow. First. There is no Evidence of Line or Genotypic Constancy or Heredity. By definition the genotype is a rigid organic entity, distinguished by breeding true from generation to generation, with the exception of mutations which are completely inherited and fluctuations which are not inherited at all. The mean of the line remains the same from generation to generation (except for rises and falls due to periodic environmental changes); the variations around these means are absolutely incapable of inheritance. Roemer and his supporters of course assume this to be true for the Pisum series dealt with, but no fragment of evidence is adduced to show either (a) that these means remain the same from generation to generation, or (b) that selection within the pure line is ineffective. The condition is even worse than this. Roemer measured the "The cardinal points of the genotype theory have been tersely, and I believe fairly, summarized elsewhere in these pages. See Amee. Nat., Vol. 45, pp. 346-363, 1911. characters of the parent plants which furnished the seed from which his various pure lines were grown, but he neither determines whether there is any parental correlation in the population nor gives us the data from which this might be determined. To be sure, one may determine from his data that the variability within the individual line is less than that of the population, but this might be as easily attributed to the much-scouted "Galton's Law" as to genotypic heredity; possibly it is to be referred to some factor qui...