No one supposes that all the individuals of the same species are cast in the very same mould. These individual differences are highly important for us, as they afford materials for natural selection to accumulate, in the same manner as man can accumulate in any given direction individual differences in his domesticated productions.
Origin 1859, 45
I am strongly inclined to suspect that the most frequent cause of variability may be attributed to the male and female reproductive elements having been affected prior to the act of conception. Several reasons make me believe in this; but the chief one is the remarkable effect which confinement or cultivation has on the functions of the reproductive system.
Origin 1859, 8
The number and diversity of inheritable deviations of structure, both those of slight and those of considerable physiological impor tance, is endless…. No breeder doubts how strong is the tendency to inheritance: like produces like is his fundamental belief.
Origin 1859, 12
I have hitherto sometimes spoken as if the variations—so common and multiform in organic beings under domestication, and in a lesser degree in those in a state of nature—had been due to chance. This, of course, is a wholly incorrect expression, but it serves to acknowledge plainly our ignorance of the cause of each particular variation.
Origin 1859, 131
I venture to advance the hypothesis of Pangenesis, which implies that the whole organisation, in the sense of every separate atom or unit, reproduces itself. Hence ovules and pollen-grains,—the fertilised seed or egg, as well as buds,—include and consist of a multitude of germs thrown off from each separate atom of the organism.
Variation, vol. 2, 357–58
These granules for the sake of distinctness may be called cell-gemmules, or, as the cellular theory is not fully established, simply gemmules. They are supposed to be transmitted from the parents to the offspring, and are generally developed in the generation which immediately succeeds, but are often transmitted in a dormant state during many generations and are then developed.
Variation, vol. 2, 374
The existence of free gemmules is a gratuitous assumption, yet can hardly be considered as very improbable, seeing that cells have the power of multiplication through the self-division of their contents…. The gemmules in each organism must be thoroughly diffused; nor does this seem improbable considering their minuteness, and the steady circulation of fluids throughout the body.
Variation, vol. 2, 378, 379
This principle of Reversion is the most wonderful of all the attributes of Inheritance…. What can be more wonderful than that characters, which have disappeared during scores, or hundreds, or even thousands of generations, should suddenly reappear perfectly developed, as in the case of pigeons and fowls when purely bred, and especially when crossed; or as with the zebrine stripes on dun-coloured horses, and other such cases?
Variation, vol. 2, 372, 373
When we hear it said that a man carries in his constitution the seeds of an inherited disease, there is much literal truth in the expression.
Variation, vol. 2, 404
I wish I had known of these views of Hippocrates, before I had published, for they seem almost identical with mine—merely a change of terms—& an application of them to classes of facts necessarily unknown to this old philosopher. The whole case is a good illustration of how rarely anything is new.—The notion of pangenesis has been a wonderful relief to my mind, (as it has to some few others) for during long years I could not conceive any possible explanation of inheritance, development &c &c, or understand in the least in what reproduction by seeds & buds consisted. Hippocrates has taken the wind out of my sails, but I care very little about being forestalled
Darwin to William Ogle,
6 March [1868], DCP 5987
Pangenesis has very few friends, so let me beg you not to give it up lightly. It may be foolish parental affection, but it has thrown a flood of light on my mind in regard a great series of complex phenomena.
Darwin to T. H. Farrer,
29 October [1868], DCP 6435
In the earlier editions of my “Origin of Species” I probably attributed too much to the action of natural selection or the survival of the fittest. I have altered the fifth edition of the Origin so as to confine my remarks to adaptive changes of structure. I had not formerly sufficiently considered the existence of many structures which appear to be, as far as we can judge, neither beneficial nor injurious; and this I believe to be one of the greatest oversights as yet detected in my work.
Descent 1871, vol. 1, 152
I have lately i.e. in new Edit, of Origin been moderating my zeal, & attributing much more to mere useless variability.
Darwin to A. R. Wallace,
27 March [1869], DCP 6684
I am aware that my view [on pangenesis] is merely a provisional hypothesis or speculation; but until a better one be advanced, it may be serviceable by bringing together a multitude of facts which are at present left disconnected by any efficient cause. As [William] Whewell, the historian of the inductive sciences, remarks:—“Hypotheses may often be of service to science, when they involve a certain portion of incompleteness, and even of error.”
Variation, vol. 2, 357
When, therefore, Mr. Galton concludes from the fact that rabbits of one variety, with a large proportion of the blood of another variety in their veins, do not produce mongrelised offspring, that the hypothesis of Pangenesis is false, it seems to me that his conclusion is a little hasty. His words are, “I have now made experiments of transfusion and cross circulation on a large scale in rabbits, and have arrived at definite results, negativing, in my opinion, beyond all doubt the truth of the doctrine of Pangenesis.” If Mr. Galton could have proved that the reproductive elements were contained in the blood of the higher animals, and were merely separated or collected by the reproductive glands, he would have made a most important physiological discovery.
Darwin 1871, 503