THE INTERLUDE OF CANCER
125
was
ultimately replaced by a corresponding, but differently developed, organ of
the adult form (sexual generation). For a variety of reasons, into which space
forbids entry here, it soon became clear to the writer that Kleinenberg’s
doctrine was inadequate, and that, instead of a substitution of organs; there
was in development in reality a substitution of organisms. The sexual organism
replaced the asexual one. This was seen to be an alternation of generations,
and as there was no homology or close likeness between the asexual generation
or its organs and the sexual form or its organs, it was an antithetic
alternation of generations.*
Now
that we have the mention of the word “antithetic,” it may be permitted in
passing to point out how Pasteur’s researches started in the antithesis of the
two sorts of tartrate crystals: mine in that of two nervous systems in the
life-history of a fish. Here we are dealing with anatomical antithesis ; later
we shall come to recognize physiological antithesis—that of two ferments.
The
tracing of the asexual generation in the backboned animals or vertebrata, from
fishes to man, was not without its own special difficulties. These were due
rather to expecting too much, and to failing at first to realize that the
higher one ascended in the scale of life, the greater became the organization
of the sexual form or generation, and the more insignificant the asexual one,
until in the highest animals, the mammals and man, the asexual generation
became reduced to the almost structureless chorion or trophoblast, as Professor
A. W. Hubrecht named it in 1889. Many people, quite ignorant of all the
embryological advances of recent years, appear to imagine that I not only
introduced the
* See Appendix C,
“The Metazoan Life-Cycle and Alternation of Generations.”