appeared, the great difficulties I felt in accepting natural selection as any real origin of species lay, first, in the seeming impossibility of the histological minutiæ of the organs in adaptation having been selected together; and, secondly, in the idea that all those wonderful and "purposeful" structures which Paley thought could only have been "designed," could be the ultimate result of any number of accidental and apparently at first "purposeless" variations. In a broad sense natural selection seemed obviously true; for Geology had revealed the fact that the world had been peopled over and over again by old forms dying out and new forms coming in; so that although it might account for the extinction of the former, it did not seem to me capable to account for the origin of the latter. I, therefore, still looked to the environment as affording a better clue to the source of variations.*

In 1869, when watching a large humble-bee hanging on to the dependent stamens of Epilobium angustifolium, the idea first occurred to me that insects themselves might be the real cause of many peculiarities in the structure of flowers. The thought passed through my mind that the way the stamens hung down might perhaps have become an hereditary effect from the repeatedly applied weight of the bees.

In 1877, I advanced this idea as a speculation

*See Letter to Nature, vol. v., p. 123.

when suggesting the origin of nectaries and irregularities of flowers in my paper on "Self-fertilisation of Flowers."

In 1880, Mr. A. R. Wallace reviewed Dr. Aug. Weismann's "Studies in the Theory of Descent."† In this work the author says: "According to my view, transmutation by purely internal causes is not to be entertained. . . . The action of external inciting causes is alone able to produce modifications." Mr. Wallace adds that he had "arrived at almost exactly similar conclusions."

In 1881, when reviewing Paul Janet's work on "Final Causes," I took occasion to remark that "I regarded the environment as by far the most important "cause" of variations, in that it influences the organism, which, by its inherent but latent power to vary, responds to the external stimulus, and then varies accordingly."

In 1881, appeared the first really systematic treatise that I know of, by Dr. C. Semper,§ which dealt with the origin of variations in animals as being referable to the environment.

In 1884, Dr. A. de Bary's "Comparative Anatomy of the Vegetative Organs of the Phanerogams and Ferns,"

*Trans. Lin. Soc., 2nd ser., Bot., vol. i., p. 317.

† Nature, xxii., p. 141.

Modern Review, 1881, p. 53.

§ The Natural Conditions of Existence as they affect Animals," Intern.

Sci. Ser., vol. xxxi.

was published in English. In the Introduction, the author writes as if it were a perfectly well understood thing that species have arisen by adaptations to the influences of the environment.*

In 1886, Mr. Herbert Spencer contributed two articles on "The Factors of Organic Evolution" to the Nineteenth Century. In these he showed, from many passages in Mr. Darwin's works, especially "Animals and Plants under Domestication" and in his later volumes, that he became much more favourably inclined to the belief that the effects of the environment were accumulative, and that in the course of some generations the variations set up tended to cease and become fixed. Mr. Spencer particularly notes the change of view, as illustrated by the expression "little doubt" being replaced by "no doubt' in the following sentence: "I think there can be no doubt that use in our domestic animals has strengthened and enlarged certain parts, and disuse diminished them; and that such modifications are inherited." It may be added that in "The Cross and Self Fertilisation of Flowers" (1876), and in "Forms of Flowers" (1877), Mr. Darwin makes many observations upon the effects of the external conditions upon plants as influencing and modifying them in various ways. It is curious to note that the three influences upon which Lamarck laid *See, e.g., p. 25. + See p. 570 and p. 749. "Use" and "disuse" in animals corresponds to what I have called "hypertrophy" and "atrophy" in plants, in this work.

emphasis are just those which Mr. Darwin himself latterly, though often indirectly perhaps, laid stress upon in his experiments, viz. crossing, use and disuse, and the physical conditions of life.

In 1886, also appeared an article in Nature, entitled, "Plants considered in Relation to their Environment." It was not signed, but the author alludes to the external conditions as bringing about all sorts of changes in the vegetative system. He stops short of discussing floral structures.

In 1886, Dr. Vines' " Physiology of Plants" appeared. After discussing various views and theories of reproduction, he observes, that “variability was first induced as the response of the organism to changes in the conditions of life."* We conclude, then, that the production of

varieties is the result of the influence of the conditions of life. †

In the last page of his work, Dr. Vines calls attention to Naegeli's view as follows: "Naegeli suggests, and his suggestion is worthy of serious consideration, that there is an inherent tendency to a higher organisation, so that each succeeding generation represents an advance,. . . as in cases of what is termed saltatory evolution." Thus,

* Page 676. Dr. Vines here uses almost identically the same words as myself in 1881. I have just found that Mr. St. G. Mivart said much the same in 1870, Genesis of Species, p. 269. See also O. Schmidt's Doctrine of Descent and Darwinism, p. 175.

+ Page 679.

while Mr. Darwin seems at last to have tacitly accepted Lamarck's ideas, at least to a considerable extent, we have here a return in 1887 to the views of the author of the "Vestiges" of 1884.

1888. I have attempted in the present work to return to 1795, and to revive the "Monde ambiant" of Geoffroy Saint Hilaire, as the primal cause of change. My object is to endeavour to refer every part of the structures of flowers to some one or more definite causes arising from the environment taken in its widest sense. To some extent the attempt must be regarded as speculative; and, therefore, any deductive or à priori reasonings met with must be considered by the reader as being suggestive only.