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.

Two years work wasted, I have been breeding those flies for all that time and I've got nothing out of it.

Within 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.