contribution to philosophical ontogeny was his 'Theory of Cellular tissues' which appeared in 1885. The group upon which most of his labor was spent and in the discussion of which he was recognized as facile princeps, is that of the tetrabranchiate cephalopods, popularly known as ammonites, which in early geological ages attained such a marvelous development. More than in many other mollusks the organization of the ammonite is reflected in the characters of the shell and the infancy, maturity and decline of the group to which it belongs is, to the qualified student, pictured in the characteristics of the successive portions of the lustrous coil of the fossil shell. By removing successive portions of these involving symmetrical whorls, the characters of the animal, from the larval stages to senile decay, may be unfolded. Hyatt's researches among these animals set the pace for the most eminent students of the group throughout the scientific world, and his most important publications were devoted to them. With an audience of perhaps a dozen living men who were fully qualified to appreciate the minutiae of his studies, it was not likely that their value could be popularly estimated. But the principles worked out were of far-reaching importance for the students of evolution everywhere, and will bear fruit in the future. A series of similar evolutionary studies of the land shells of the Hawaiian Islands was nearly completed at the time of his death.
Hyatt's studies of evolution, in geologic time, as well as on existing animals, led him to what are sometimes called Neo-Lamarckian conclusions. He believed in the hereditary transmission of acquired characters, and, in one case at least, proved their transmission. In common with Cope and the majority of American zoologists who have not derived their prepossessions from exotic teachers, he pursued the ideas of Lamarck and Darwin to their logical conclusion, as revealed in the genetic history of the animals he studied, and added to them a body of evolutionary philosophy with which all schools will have to reckon.
Leaving a subject which verges on the present conflict of scientific theories, it remains to say a few words, all too inadequate, on the man whom we have lost. No one who had the privilege of Hyatt's acquaintance but will' join in testimony to his high-minded scientific integrity; the infectiousness of his hearty enthusiasm; the fertility of his imagination, which yet was always controlled by constant reference to experience and observation; and the general atmosphere of good fellowship which he diffused. Unpretentious, open-minded, a constant example of clean living, high thinking, and unassuming kindness to all about him, an ideal husband and father, a steadfast friend; we shall not soon look upon his like again.
Professor Hyatt leaves a widow, a son and two daughters, whom the sympathy of his colaborers in two hemispheres may in some slight degree sustain under the consciousness of their common loss.