File:The American Museum journal (c1900-(1918)) (18134286286).jpg

Title: The American Museum journal
Identifier: americanmuseumjo16amer (find matches)
Year: c1900-(1918) (c190s)
Authors: American Museum of Natural History
Subjects: Natural history
Publisher: New York : American Museum of Natural History
Contributing Library: American Museum of Natural History Library
Digitizing Sponsor: Biodiversity Heritage Library

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242 THE AMERICAN MUSEUM JOURNAL bearing the X chromosomes: they will, when uniting with an egg, produce female individuals and, since half of the eggs have the factor for red while the other half have the factor for white, half of the resulting females will be pure red, while the other half will be hybrid, but will have red eyes because red is domi- nant over white. In other words, all of the females of this generation show red eyes. When the sperm lacking X chro- mosomes unites with the eggs, half of which have the factor for red in their X chromosomes and the other half white, the result will be males, half of which will be pure red and the other half of which will be pure white. This gives us the result stated above; namely, all the females and half of the males red-eyed while the other half of the males are white-eyed. This case may perhaps be more readily understood by reference to page 240, and page 241 shows the details of the seconfl case mentioned above, which involves what is known as " criss- cross" inheritance. The relatively complicated " sex- \ C^- linked" inheritance just explained be- came simple when the explanation was found, and comes near to demonstrating that there is a relation between heritable characters and chromosomes. It would probal)ly be carrying scientific scepticism too far to continue doubting that it is a causal relation. Ordinary Mendelian characters, that is, those which come out in F2 in the 3:1 ratio, are related to or borne by the ordinary chromosomes, that is, those chromosomes which are alike and paired in each sex. The interested reader may make diagrams, similar to the ones given here, which will show the mechanism graphically. Now that we think we know where the something which transmits a given character lies in the germ cell, we begin to wonder harder than ever what that something is and how it does it. A number of big steps have been taken in the explanation of heredity and, although the goal is still far ahead, by looking back over the ground already covered we are encour- aged to belie^■e that it will finally be reached. 1^ PARENTS 1
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