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38 with there are no subsequent generations! These facts cannot be too strongly insisted on, and should be carefully considered by those geologists who lay so much stress on appearances, and assume that a transmission of acquired characters is a demonstrable process, because in many or even in most cases it looks just as if the disappearance were a direct consequence of disuse:—appearances are often deceitful and therefore cannot be accepted in place of facts. We might as well maintain that the sun goes round the earth: better proofs to the contrary could not, I believe, be adduced in this case than are brought forward with regard to the facts just stated in connexion with the transmission of acquired characters.

We can therefore in this case only ascribe the degeneration of the reproductive organs to processes of selection: and there can be no objection to this view, for the degeneration is an advantageous arrangement, by means of which the workers were fitted to give their whole strength to work. The advantage to the colony of possessing a worker-caste has been so often shown that I need not here go into details.

A further question now arises as to how it is conceivable that two or even three kinds of primary constituents of the organs in question should be contained in one germ, and how they could have become developed. This seems to me not to present much difficulty on the principles of my theory of heredity. I suppose that the germ·plasm includes a considerable number of secondary units, each of which contains within itself all the primary constituents that