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THROUGH INSECT AND OTHER AGENCIES
REV. GEORGE HENSLOW
M.A., F.L.S., F.G.S.
PROFESSOR OF BOTANY, QUEEN'S COLLEGE
AUTHOR OF “EVOLUTION AND RELIGION,” “CHRISTIAN BELIEFS RECONSIDERED
“BOTANY FOR CHILDREN,” “FLORAL DISSECTIONS," ETC.
WITH EIGHTY-EIGHT ILLUSTRATIONS
KEGAN PAUL, TRENCH & CO., 1, PATERNOSTER SQUARE
The belief that we must look mainly to the environment as furnishing the influences which induce plants to vary in response to them—whereby adaptive morphological (including anatomical) structures are brought into existence-appears to be reviving. To illustrate the progress of this belief, I will give a few cases.
In 1795, Geoffroy Saint Hilaire“ seems to have relied chiefly on the conditions of life, or the 'monde ambiant,' as the cause of change."
In 1801, Lamarck "attributed something to the direct action of the physical conditions of life” as the means of modification, "something to the crossing of already existing forms, and much to use and disuse."
In 1831, Mr. Patrick Matthew (who, like Dr. W. C. Wells in 1818, anticipated Mr. Darwin in the theory of “natural selection ") seems to have attributed much influence to the direct action of the conditions of life.”
* I quote from Mr. Darwin's "Historical Sketch" in his Origin of Species, 6th ed., 1878.
In 1844, the “ Vestiges of Creation" appeared. The author suggests that “impulses” were imparted to the forms of life, on the one hand advancing them, and on the other hand tending to modify organic structures in accordance with external circumstances; the effects thus produced by the conditions of life being gradual.
In 1852, Mr. Herbert Spencer "attributed the modifications [of species] to the change of circumstances.”
In 1859, “The Origin of Species” appeared. Mr. Darwin did not at first seem to lay so much stress as his predecessors upon the action of the environment as a cause, for he says: “It is curious how largely my grandfather, Dr. Erasmus Darwin, anticipated the views and erroneous grounds of opinion of Lamarck.” Again, in speaking of the constancy of some varieties, he says, “Such considerations incline me to lay less weight on the direct action of the surrounding conditions, than on a tendency to vary, due to causes of which we are quite
He had, however, previously said, “ Changed conditions of life are of the highest importance in causing variability. .
.... It is not probable that variability is an inherent and necessary contingent under all circumstances." +
With regard to my own opinion, having been early and greatly interested in Paley's “Natural Theology," as well as the “ Vestiges” when Mr. Darwin's work
* Or. of Sp., p. 107.
+ Ibid., p. 31. See also Desc. of Man, ii., p. 388.