Here, then, deterioration as to size of structure (wings of birds), and deterioration as to complexity of structure (brain and eyes) are expressly put upon the same footing. Therefore, if in the latter case the "tendency to deterioration" does not "demand an explanation," beyond the fact that the hitherto maintaining influence has been withdrawn, neither is any such further explanation demanded in the former case. Which is exactly my own view of the matter. It is also Mr. Galton's view. For although, in the passage formerly quoted, Professor Lloyd Morgan appears to think that by the phrase "Regression to Mediocrity" Mr. Galton means to indicate that panmixia can cause degeneration only as far as the mediocrity level of the first generations, this, in point of fact, is not what Galton means, nor is it what he says. The phrase in question occurs "in another connexion," and, indeed, in a different publication. But where he expressly alludes to the cessation of selection, this is what he says. The italics are mine. "A special cause may be assigned for the effects of use in causing hereditary _atrophy_ of disused parts. It has already been shown that all exceptionally developed organs tend to deteriorate: consequently, those that are not _protected_ by selection will _dwindle_. The level of muscular efficiency in the wing of a strongly flying bird [curiously enough, the same case that is chosen by Professor Lloyd Morgan to illustrate his opposite view], is like the level of water in the leaky vessel of a Danaid, only secured to the race by _constant effort_, so to speak. _Let the effort be relaxed ever so little, and the level immediately falls[145]._" [145] _A Theory of Heredity_, Journal of Anthropological Institute, 1875. Vol. v. p. 345.