My dear Sir
I shd. expect that the period of gestation would differ very little in the individuals of the same species, as long as its conditions of life remain the same.2 But I doubt whether it wd. serve as an absolute criterion; for although little or nothing on this head can be known with respect to species in a state of nature, yet with races of the same species, as with dogs & cattle, the period is known slightly to differ. In the germination of seeds from the same capsule there is often the most wonderful & inexplicable difference in the periods.
With my thanks for your kindness, I remain | My dear Sir | Yours very faithfully | Ch. Darwin
Please cite as “DCP-LETT-7992,” in Ɛpsilon: The Charles Darwin Collection accessed on