there is throughout the metazoa a general
correlation between the natural lifetime of individuals composing any
given species, and the age at which they reach maturity or first become
capable of procreation." This, I believe, has been the conclusion
generally arrived at by biologists for some years past.

Lateness, then, in the average age of reproduction appears to be the
principle underlying longevity. There does not appear at first sight to
be much connection between such distinct and apparently disconnected
phenomena as 1, the orderly normal progress of development; 2, atavism
and the resumption of feral characteristics; 3, the more ordinary
resemblance _inter se_ of nearer relatives; 4, the benefit of an
occasional cross, and the usual sterility of hybrids; 5, the
unconsciousness with which alike bodily development and ordinary
physiological functions proceed, so long as they are normal; 6, the
ordinary non-inheritance, but occasional inheritance of mutilations; 7,
the fact that puberty indicates the approach of maturity; 8, the
phenomena of middle life and old age; 9, the principle underlying
longevity. These phenomena have no conceivable bearing on one another
until heredity and memory are regarded as part of the same story.
Identify these two things, and I know no phenomenon of heredity that does
not immediately become infinitely more intelligible. Is it conceivable
that a theory which harmonises so many facts hitherto regarded as without
either connection or explanation should not deserve at any rate
consideration from those who profess to take an interest in biology?

It is not as though the theory were unknown, or had been condemned by our
leading men of science. Professor Ray Lankester introduced it to English
readers in an appreciative notice of Professor Hering's address, which
appeared in _Nature_, July 18, 1876. He wrote to the _Athenaeum_, March
24, 1884, and claimed credit for having done so, but I do not believe he
has ever said more in public about it than what I have here referred to.
Mr. Romanes did indeed try to crush it in _Nature_, January 27, 1881, but
in 1883, in his "Mental Evolution in Animals," he adopted its main
conclusion without acknowledgment. The _Athenaeum_, to my unbounded
surprise, called him to task for this (March 1, 1884), and since that
time he has given the Heringian theory a sufficiently wide berth. Mr.
Wallace showed himself favourably enough disposed towards the vi