Heredity, health and personal beauty / by John V. Shoemaker.

Date:
1890
Catalogue details

Licence: Public Domain Mark

Credit: Heredity, health and personal beauty / by John V. Shoemaker. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    affirms it with singular conclusiveness, because he is repudiating there the representation that had been made by his critics to the contrary effect. In the preface to the second edition of “ The Descent of Man ” he says :— I may take this opportunity of remarking that my critics frequently assume that I attribute all changes of corporeal structure and mental power exclusively to the natural selection of such variations as are often called spontaneous; whereas, even in the first edition of “ The Origin of Species,” I distinctly stated that great weight must be attributed to the inherited effects of use and disuse with respect both to the body and mind. If natural selection stopped short at putting stress upon organisms, even the forms most susceptible of correlated change might not be capable of resisting death. But, assuming within an exterior change at least temporary endurance of the new conditions, no organism, without use and disuse of existing parts, could rise or fall, in function or structure, above or below the forms best adapted to survive at the time of the changed conditions. The fittest at that, time, if they survived, would remain through their descendants, if the exterior conditions did not again change, the fittest for all time to survive. There would be no evolution,—that is, no development to higher or lower forms: their status would be permanently fixed. An aquatic animal could not have become a terrestrial one, nor a terrestrial one, as in the case of the placental mammal, the whale, an aquatic one. Nature can modifj^ nothing to the extent of making it a new creation merely by putting stress upon it. Stress is more than negative : it represents opposition where it does not represent . antagonism. Opposition does not of itself create by the slowest, or any, process. Only, as from the effects of use and disuse of parts in changing function and structure, is it possible to con- ceive of organisms subjected to change in environment continu- ing to live with different aspects under changed conditions. We have already remarked of the second learned gentleman’s