riations have to
climatal conditions.

Do you think there are many such cases? Does Oxalis corniculata present
exactly the same varieties under very different climates?

How is it with any other British plants in New Zealand, or at the foot
of the Himalaya? Will you think over this and let me hear the result?

One other question: do you remember whether the introduced Sonchus in
New Zealand was less, equally, or more common than the aboriginal stock
of the same species, where both occurred together? I forget whether
there is any other case parallel with this curious one of the Sonchus...

I have been making good, though slow, progress with my book, for facts
have been falling nicely into groups, enlightening each other.

LETTER 57. TO T.H. HUXLEY. Moor Park, Farnham, Surrey [1857?].

Your letter has been forwarded to me here, where I am profiting by a
few weeks' rest and hydropathy. Your letter has interested and amused me
much. I am extremely glad you have taken up the Aphis (57/1. Professor
Huxley's paper on the organic reproduction of Aphis is in the "Trans.
Linn. Soc." XXII. (1858), page 193. Prof. Owen had treated the subject
in his introductory Hunterian lecture "On Parthenogenesis" (1849).
His theory cannot be fully given here. Briefly, he holds that
parthenogenesis is due to the inheritance of a "remnant of spermatic
virtue": when the "spermatic force" or "virtue" is exhausted fresh
impregnation occurs. Huxley severely criticises both Owen's facts and
his theory.) question, but, for Heaven's sake, do not come the mild
Hindoo (whatever he may be) to Owen; your father confessor trembles for
you. I fancy Owen thinks much of this doctrine of his; I never from
the first believed it, and I cannot but think that the same power is
concerned in producing aphides without fertilisation, and producing, for
instance, nails on the amputated stump of a man's fingers, or the new
tail of a lizard. By the way, I saw somewhere during the last week or
so a statement of a man rearing from the same set of eggs winged and
wingless aphides, which seemed new to me. Does not some Yankee say that
the American viviparous aphides are winged? I am particularly glad that
you are ruminating on the act of fertilisation: it has long seemed to me
the most wonderful and curious of physiological problems. I have
often and often speculated for amusement on the subject, but quite
fruitlessly. Do you not think that the conjugation of the Diatom