NOTICES OF BIOGRAPHICAL MEMOIRS 
737 
variations in nutrition or reproduction which would lead representatives 
of the first family to live after the manner of the second. Reason has 
already been given for supposing that convergence in color would ac- 
company convergence in habit. 
Whatever may eventually prove to be the case with the problem of 
mimetic resemblance, the observations presented in this abstract em- 
body a great mass of fact whose theoretical significance is obvious. It 
undermines many speculative explanations of animal coloration in terms 
of natural selection, but, being itself consistent with the Darwinian 
hypothesis, it replaces them by something which may not be lightly 
dismissed from consideration. It emphasizes the common occurrence 
among animals of attributes of apparent advantage to them, and forces 
the issue between natural selection and the inheritance of acquired 
characters as the immediate cause of adaptation. 
NOTICES OF BIOGRAPHICAL MEMOIRS 
The following biographical memoirs have been published by the Academy 
since the last notices of such memoirs appeared in the November, 1915, 
number of the Proceedings. 
George William Hill (1838-1914). By Ernest W. Brown. Biographical 
Memoirs of the National Academy , 8, pp. 275-309. 
This Memoir discusses the life-work of George W. Hill along the following outline: Boy- 
hood, First papers; Influence of Delaunay and Hansen, Comet of 1858, Elements of Venus, 
the Years 1872-1875; the Great Decade 1875-1885, Hill's Mental Development, Astronomy 
before Hill, the Two Great Memoirs of 1877, Influence of Euler, the Periodic Orbit, Sta- 
bility, Infinite Determinants, Relation to J. C. Adams' Work, Theories of Jupiter and 
Saturn, Estimate by F. R. Moulton; Residence in Washington, Application of the Methods 
of Delaunay, Hansen, de Pontecoulant, and Gauss; Concluding years, Hill's Characteristics, 
Estimates by Poincare, R. S. Woodward, A. S. Flint, H. B. Hedrick, and H. Jacoby; Hill's 
Scientific Honors; Bibliography. 
Theodore Nicholas Gill (1837-1914.) By Wiliam Healey Dall. 
Biographical Memoirs of the National Academy, 8, pp. 313-343. 
This Memoir recounts the life-work of Theodore N. Gill: Boyhood, Report on the Fishes 
of New York, Trips to the Antilles and Newfoundland; Connections with the Smithsonian 
Institution, the Library of Congress, and the U. S. Fish Commission; Editor of the Osprey 
Work on MoUusca; Estimates by the Commissioner of Fisheries, by the Director of the Na- 
tional Museum; Associations with George Washington University; Personal Characteristics; 
Bibliography. 
