or complete exposition of the subject, it is merely an attempt to state
the fundamental facts and conclusions, the importance of which it seems to
me are not generally appreciated by biologists.

I have reviewed some of the chief of the recent discoveries concerning
mutations, Mendelism, chromosomes, etc., but have not thought it necessary
to repeat the illustrations which are contained in many of the volumes to
which I have referred. I have made some Mendelian experiments myself, not
always with results in agreement with the strict Mendelian doctrine, so
that I am not venturing to criticise without experience. I have not
hesitated to reprint the figure, published many years ago, of a Flounder
showing the production of pigment under the influence of light, because I
thought it was desirable that the reader should have before him this
figure and those of an example of mutation in the Turbot for comparison
when following the argument concerning mutation and recapitulation.

I take this opportunity of expressing my thanks to the Councils of the
Royal Society and the Zoological Society for permission to reproduce the
figures in the Plates. I also desire to thank Professor Dendy, F.R.S., of
King's College for his sympathetic interest in the publication of the
book, and Messrs. Constable and Co. for the care they have taken in its
production.

J. T. CUNNINGHAM.
London, _June_ 1921.



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