Note 7 — Chapter XXV · LAWS OF VARIATION, continued.—CORRELATED VARIABILITY.
Reading edition
Naturalists differ with respect to the homologies of the digits of birds; but several uphold the view above advanced. See on this subject Dr. E. S. Morse in ‘Annals of the Lyceum of Nat. Hist. of New York,’ vol. x. 1872, p. 16.