frightened by his sharp cleverness: to know him more was to be attracted by it: to know him well was to love and admire the goodness which kept such cleverness in such control.

I.

WEISMANN'S ESSAYS UPON HEREDITY,

ETC.1

IT is certainly not too much to say that Professor Weismann's "Essays on Heredity," are the most important contribution to speculative biology which has been made since the "Origin of Species" was published. Yet, except to professed biologists, Professor Weismann's work has till lately been little known in England. Attention was first drawn to it by an article, entitled "Death,” in the Nineteenth Century for May, 1885, by Mr. A. E. Shipley; this was followed up by two excellent articles in Nature by Professor Moseley, which gave in summary the main conclusions arrived at; and in 1887, at the Manchester meeting of the British Association, Professor Weismann himself took part in a discussion introduced by Professor Ray Lankester, on "The Transmission of Acquired Characters."

1 Essays upon Heredity, etc. By Professor August Weismann. Edited by Edward B. Poulton, M.A., F.R.S., etc., Tutor of Keble College, Oxford, Dr. Schönland, Ph. D., and A. E. Shipley, M.A. Oxford; Clarendon Press.

B

As far back as 1884, Mr. A. E. Shipley began a translation of the two essays which stand first in the present collection, and he has now co-operated with Mr. E. B. Poulton and Dr. Schönland in preparing the volume before us. Professor Weismann has himself looked over the proof-sheets, which is a sufficient guarantee for the accuracy of the work as a whole, while the essays in their English dress admit of the high commendation that, if it were not for the necessary insertion in brackets of a German technical term here and there, there would be nothing to remind us that the essays are a translation at all.

The essays themselves are eight in number, and are arranged in chronological order, the first being written in 1881, the last in 1888. We are thus able to trace the development of the theory in Professor Weismann's own thoughts, and see how he was led from point to point, till he reached the central position, that in what he calls "the continuity of Germ-plasm" is to be found the true explanation of heredity. And this involves the non-transmission of acquired characters, and the overthrow of the Lamarckian and Neo-Lamarckian theory.

It is only the outside of Professor Weismann's work that we can hope to touch in the present review. And even then we can do little more than state results. For the evidence lies in the mysterious processes of embryological development, a

discussion of which would be as much out of place as it would be beyond our power to attempt.

There are two centres round which Professor Weismann's investigations turn-a speculation as to the origin of natural death, and a new theory of heredity, and the two are closely connected together, and result in a complete and coherent biological theory.

1. The first essay raises the question of the reason of the great variation in the duration of life among plants and animals. Can this variation be brought under any law? It is assumed, to start with, that duration of life depends upon adaptation to external conditions, and is governed by the needs of the species rather than of the individual. When, then, the individual becomes useless to the species, whether that stage is reached after a longer or a shorter period, we should expect him to have reached the natural term of his life. And we are confirmed in this expectation by finding that, as a rule, life does not greatly outlast the period of reproduction, except in those species which tend their young. In spite of the fact that there is very little accurate information available as to the duration of life in different species, Professor Weismann is able to produce some remarkable statistics in favour of this view, the most striking perhaps being drawn from the "exceptions" which "prove the rule." But this discussion of the duration of life

leads on to the extremely interesting question of the meaning and nature of death. Science has in past days discussed the origin of life, and for the present has put the question aside as an insoluble problem. On this matter, then, Professor Weismann has nothing to say beyond recording his belief that "spontaneous generation, in spite of all vain efforts to demonstrate it, remains a logical necessity." But on the phenomenon of death he has much to tell us. And his conclusions are as striking as they are suggestive.

It sounds at first like a paradox to say that "it is only from the point of view of utility that we can understand the necessity of death," or to talk about death as " a beneficial occurrence," an "adaptation," which has arisen by the operation of natural selection, because a life of unlimited duration would be "a luxury without a purpose." Still more startling is it to be told that, though the higher organisms "contain within themselves the germs of death," there are inferior organisms which are "endowed with the potentiality of never-ending life." But it is only the language which is paradoxical. When the amoeba increases by division, neither half is younger or older than the other. The process may go on for centuries; thousands of amoebae may be destroyed, yet the amoebae who survive are as old as, for they are identical with, the first amoeba. The same is true of the