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.

    29/228 page 15
    They are accidents, it is true, but they are causal accidents. In his famous book on Animals and Plants under Domestication, Darwin dwells at great length on the nature of the conditions that bring about varia¬ tions. If some of his views seem to 11s today at times vague, at times problematical, and often without a secure basis, nevertheless we find, in every instance, that Darwin was searching for the physical causes of variation. He brought, in consequence, conviction to many minds that there are abundant indications, even if certain proof is lacking, that the causes of variation are to be found in natural processes. Today the belief that evolution takes place by means of natural processes is generally accepted. It did not seem probable that we should ever again have to renew the old contest between evolution and spe¬ cial creation. But this is not enough. We can never remain satis¬ fied with a negative conclusion of this kind. We must find out what natural causes bring about variations in animals and plants; and we must also find out what kinds of variations are inherited, and how they are inherited. If the circumstantial evidence for or¬ ganic evolution, furnished by comparative anatomy, embryology and paleontology is cogent, we should expect to observe evolution going on at the present time, i.e., we should be able to observe the occurrence of variations and their transmission. This has actu-
    digitised image 1
    digitised image 2
    digitised image 3