Life and Letters of Charles Darwin, volume 2 includes the following letter from Darwin to Charles Lyell, written about a review of his new book:
P.S.—I must tell you one little fact which has pleased me. You may remember that I adduce electrical organs of fish as one of the greatest difficulties which have occurred to me, and — notices the passage in a singularly disingenuous spirit. Well, McDonnell, of Dublin (a first-rate man), writes to me that he felt the difficulty of the whole case as overwhelming against me. Not only are the fishes which have electric organs very remote in scale, but the organ is near the head in some, and near the tail in others, and supplied by wholly different nerves. It seems impossible that there could be any transition.
I can't get the whole meaning of this bolded phrase, though I know the meaning of "remote" and "scale".
Does it mean that the small and thin plates that protect the fish skin are very far from each other?