Evolution and genetics / by Thomas Hunt Morgan.

  • Thomas Hunt Morgan
Date:
1925
Catalogue details

Licence: In copyright

Credit: Evolution and genetics / by Thomas Hunt Morgan. Source: Wellcome Collection.

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    one or another of these mutations. Many different kinds of changes have taken place in the wings and several of these involve the size of the wings. If we arrange the latter arbitrarily in the order of their size there will be an almost complete series begin- Fig. 6.—Male and female vinegar fly, Dro¬ sophila melanogaster. ning with normal wings and ending with those of apterous flies. Several of these types are represented in figure 7. The order in which these mutations oc¬ curred bears no relation to their size; each originated independently from the wild tyj)e. Mutations have occurred involving the pigmen¬ tation of the body and wings. The head and thorax of the wild Drosophila melanogaster are grayish yel¬ low, the abdomen is banded with yellow and black, and the wings are gray. There have appeared in our cultures several kinds of darker types ranging to almost black flies and to lighter types that are pale yellow. If put in line a series may be made from the darkest flies at one end to the light yellow flies
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