I believe that the conditions of life, from their action on the reproductive system, are so far of the highest importance as causing variability. I do not believe that variability is an inherent and necessary contingency, under all circumstances, with all organic beings, as some authors have thought. The effects of variability are modified by various degrees of inheritance and of reversion. Variability is governed by many unknown laws, more especially by that of correlation of growth. Something may be attributed to the direct action of the conditions of life. Something must be attributed to use and disuse.Some of this passage, the conclusion to the chapter on 'Variation under Domestication', confuses me. I get the impression that what I understand by variation is a more general meaning than that used in this passage.
I also do not know quite what he means by "correlation of growth".
I assume that by "conditions of life" he is talking about deaths by natural causes, and the like.
The comment on "use and disuse" sounds rather Lamarckian. I wonder if it is a throw-away comment, a nod to Lamarck's work.
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Well, I guess I should have read a bit further on...
ReplyDelete"The term 'variety' is almost equally difficult to define; but here community of descent is almost universally implied, though it can rarely be proved. ... Some authors use the term 'variation' in a technical sense, as implying a modification directly due to the physical conditions of life; and 'variations' in this sense are supposed not to be inherited : but who can say that the dwarfed condition of shells in the brackish waters of the Baltic, or dwarfed plants on Alpine summits, or the thicker fur of an animal from far northwards would not in some cases be inherited for at least some few generations? and in this case I presume that the form would be called a variety."
Well - he certainly seems to have been wanting for DNA to be discovered!