There is, besides, another difficulty. According to Weismann and yourself, it is natural selection that has brought about sexuality 'for the sake of better results in the offspring,' by making them more variable or plastic. But how can natural selection act prophetically? Unless the variability is of use to the individuals at each stage of its advance, it cannot come under the sway of natural selection, however advantageous it may eventually prove to the type. But, if one thinks about it, how can such variability be of any use to the individual? Observe, beneficial variability is quite different from beneficial variation. It is the tendency to vary that is in question, not the occurrence of this, that, and the other display of it. Now, I do not see how sexuality can have been evolved by natural selection for the purpose of securing their tendency in the future, when it can never be of any use to individuals of the present. Each individual of the present is an accomplished fact; the tendency to produce variable offspring is, therefore, of no use to it individually, and so natural selection would have no reason to pick it out for living and propagating. Such is my difficulty touching this point. Another is, why do we meet with such great differences between (sometimes) allied natural genera, and even whole natural orders, as to the facility with which their constituent species hybridise? For example, species of genus Geranium will hybridise almost better than any other, those of the Pelargonium scarcely at all.
I hope that at some time you will be able to get sent to me seeds of species peculiar to oceanic islands, should you hear of any botanists who are visiting such islands.
G. J. Romanes.
I note that you have been good enough to pass my questions on to Mr. Greene, whose great kindness (already experienced by me) will, I trust, prevent him from thinking that the failure of the seeds to flower here was due to any negligence on my part.
Yes, it is the same Rev. Mr. Gulick whom you describe that wrote the paper on 'Divergent Evolution' to which I alluded, and which is a most remarkable paper in every way, though not at all easy to master. Wallace completely misunderstood it in his letter to 'Nature.' It was his work in shells that first led Mr. Gulick to study Isolation, and he has been at work upon the subject ever since. To the best of my judgment, he has demonstrated the necessity of what he calls 'segregate breeding' for 'polytypic evolution,' and in this connection has worked out the idea of physiological selection (which he calls segregate fecundity) much more fully than I have.
It is most astonishing to me with what a storm of opposition this idea has been met in England, and how persistent is the misunderstanding. In Germany and America it is being much more fairly treated, but meanwhile I intend to keep it as quiet as possible, till I shall be in a position to publish a large body of experimental observations. As far as time has hitherto allowed, the results are strongly corroborative of the theory.
I have now read your admirable book, and my only objection to it is that it seems in such large measure to anticipate the publication of my own course of lectures on the theory of Evolution which I am now giving at the Royal Institution. But, on the other hand, this will relieve me of the necessity of printing a good deal of my matter, as it will be sufficient to refer to your book in mine when the two cover common ground. It is needless to add that I am very glad to note you think so well of physiological selection.
Yours very truly,
G. J. Romanes.
The theory of the Non-Inheritance of Acquired Characters, with which Professor Weismann's name is inseparably connected, was now coming to the front.