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I will add only that, considering the width and depth of the effects which acceptance of one or other of these hypotheses must have on our views of Life, Mind, Morals, and Politics, the question–Which of them is true? demands, beyond all other questions whatever, the attention of scientific men.

* * * * *

After the above articles were published, I received from Dr. Downes a copy of a paper “On the Influence of Light on Protoplasm,” written by himself and Mr. T.P. Blunt, M.A., which was communicated to the Royal Society in 1878. It was a continuation of a preceding paper which, referring chiefly to Bacteria, contended that–

“Light is inimical to, and under favourable conditions may wholly prevent, the development of these organisms.”

This supplementary paper goes on to show that the injurious effect of light upon protoplasm results only in presence of oxygen. Taking first a comparatively simple type of molecule which enters into the composition of organic matter, the authors say, after detailing experiments:–

“It was evident, therefore, that oxygen was the agent of destruction under the influence of sunlight.”

And accounts of experiments upon minute organisms are followed by the sentence–

“It seemed, therefore, that in absence of an atmosphere, light failed entirely to produce any effect on such organisms as were able to appear.”

They sum up the results of their experiments in the paragraph–

“We conclude, therefore, both from analogy and from direct experiment, that the observed action on these organisms is not dependent on light per se, but that the presence of free oxygen is necessary; light and oxygen together accomplishing what neither can do alone: and the inference seems irresistible that the effect produced is a gradual oxidation of the constituent protoplasm of these organisms, and that, in this respect, protoplasm, although living, is not exempt from laws which appear to govern the relations of light and oxygen to forms of matter less highly endowed. A force which is indirectly absolutely essential to life as we know it, and matter in the absence of which life has not yet been proved to exist, here unite for its destruction.”

What is the obvious implication? If oxygen in presence of light destroys one of these minutest portions of protoplasm, what will be its effect on a larger portion of protoplasm? It will work an effect on the surface instead of on the whole mass. Not like the minutest mass made inert all through, the larger mass will be made inert only on its outside; and, indeed, the like will happen with the minutest mass if the light or the oxygen is very small in quantity. Hence there will result an envelope of changed matter, inclosing and protecting the unchanged protoplasm–there will result a rudimentary cell-wall.

FOOTNOTES:

[Footnote 41: It is probable that this shortening has resulted not directly but indirectly, from the selection of individuals which were noted for tenacity of hold; for the bull-dog’s peculiarity in this respect seems due to relative shortness of the upper jaw, giving the underhung structure which, involving retreat of the nostrils, enables the dog to continue breathing while holding.]

[Footnote 42: Though Mr. Darwin approved of this expression and occasionally employed it, he did not adopt it for general use; contending, very truly, that the expression Natural Selection is in some cases more convenient. See Animals and Plants under Domestication (first edition) Vol. i, p. 6; and Origin of Species (sixth edition) p. 49.]

[Footnote 43: It is true that while not deliberately admitted by Mr. Darwin, these effects are not denied by him. In his Animals and Plants under Domestication (vol. ii, 281), he refers to certain chapters in the Principles of Biology, in which I have discussed this general inter-action of the medium and the organism, and ascribed certain most general traits to it. But though, by his expressions, he implies a sympathetic attention to the argument, he does not in such way adopt the conclusion as to assign to this factor any share in the genesis of organic structures–much less that large share which I believe it has had. I did not myself at that time, nor indeed until quite recently, see how extensive and profound have been the influences on organization which, as we shall presently see, are traceable to the early results of this fundamental relation between organism and medium. I may add that it is in an essay on “Transcendental Physiology,” first published in 1857, that the line of thought here followed out in its wider bearings, was first entered upon.]

[Footnote 44: Text-Book of Botany, etc. by Julius Sachs. Translated by A. W. Bennett and W. T. T. Dyer.]

[Footnote 45: A Manual of the Infusoria, by W. Saville Kent. Vol. i, p. 232.]

[Footnote 46: Ib. Vol. i, p. 241.]

[Footnote 47: Kent, Vol. i, p. 56.]

[Footnote 48: Ib. Vol. i, p. 57.]

[Footnote 49: The Elements of Comparative Anatomy, by T. H. Huxley, pp. 7-9.]

[Footnote 50: A Treatise on Comparative Embryology, by F. M. Balfour, Vol. ii, chap. xiii.]

[Footnote 51: Sachs, p. 210.]

[Footnote 52: Ibid. pp. 83-4.]

[Footnote 53: Ibid. p. 185.]

[Footnote 54: Ibid. 80.]

[Footnote 55: Sachs, p. 83.]

[Footnote 56: Ibid. p. 147.]

[Footnote 57: A Treatise on Comparative Embryology. By Francis M. Balfour, LL.D., F.R.S. Vol. ii, p. 343 (second edition).]

[Footnote 58: Balfour, l.c. Vol. ii, 400-1.]

[Footnote 59: Balfour, l.c. Vol. ii, p. 401.]

[Footnote 60: For a general delineation of the changes by which the development is effected, see Balfour, l.c. Vol. ii, pp. 401-4.]

[Footnote 61: See Balfour, Vol. i, 149 and Vol. ii, 343-4.]