Sixthly, those organisms that are the longest in reaching maturity should on the average be the longest-lived, for they will have received the most momentous impulse from the weight of memory behind them.  This harmonizes with the latest opinion as to the facts.  In his article of Weismann in the Contemporary Review for May, 1890, Mr. Romanes writes:  “Professor Weismann has shown that 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 harmonizes 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 13, 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 view that heredity and memory are part of the same story when he reviewed my book Life and Habit in Nature, March 27, 1879, but he has never since betrayed any sign of being