Except for the rare cases of plastid inheritance, the inheritance of all known cooacters can be sufficiently accounted for by the presence of genes in the chromosomes. In a word the cytoplasm may be ignored genetically.
Thomas Hunt MorganWithin the period of human history we do not know of a single instance of the transformation of one species into another one. It may be claimed that the theory of descent is lacking, therefore, in the most essential feature that it needs to place the theory on a scientific basis, this must be admitted.
Thomas Hunt MorganTwo years work wasted, I have been breeding those flies for all that time and I've got nothing out of it.
Thomas Hunt MorganThat the fundamental aspects of heredity should have turned out to be so extraordinarily simple supports us in the hope that nature may, after all, be entirely approachable. Her much-advertised inscrutability has once more been found to be an illusion due to our ignorance. This is encouraging, for, if the world in which we live were as complicated as some of our friends would have us believe we might well despair that biology could ever become an exact science.
Thomas Hunt Morgan