[167] Mr. Thiselton Dyer in _Nature_, _loc. cit._
That Mr. Wallace himself should be biassed in this matter might, perhaps, be expected. After rendering the following very unequivocal passage from the _Origin of Species_ (p. 72)--"There can be little doubt that the tendency to vary in the same manner has often been so strong, _that all individuals of the same species have been similarly modified without the aid of any form of selection_"--Mr. Wallace says, "But no proof whatever is offered of this statement, and it is so entirely opposed to all we know of the facts of variation as given by Darwin himself, that the important word 'all' is probably an oversight." But, if Mr. Wallace had read the very next sentence he would have seen that here the important word "all" could not _possibly_ have been "an oversight." For the passage continues,--"Or only a third, fifth, or tenth part of the individuals may have been thus affected, of which fact several instances could be given. Thus Graba estimates that about one-fifth of the guillemots in the Faroe Islands consist of a variety so well marked, that it was formerly ranked as a distinct species under the name of Uria lacrymans." And even if this passage had not been thus specially concerned with the question of the _proportion_ in which "_individuals of the same species have been similarly modified without the aid of any form of selection_" the oversight with respect to "the important word 'all'" would still have remained an oversight of a recurrent character, as the following additional quotations from other parts of Darwin's writings may perhaps render apparent.
"There must be some efficient cause for each slight individual difference, as well as for more strongly marked variations which occasionally arise; and if the unknown cause were to act persistently, it is almost certain that _all_ the individuals of the _species_ would be similarly modified[168]."
"The acquisition of a useless part can hardly be said to raise an organism in the natural scale.... We are so ignorant of the exciting cause of the above specified modifications; but if the unknown cause were to act almost uniformly for a length of time, we may infer that the result would be almost uniform; and in this case _all_ the individuals of the _species_ would be modified in the same manner[169]."