able a teacher as Hyatt should have left so few disciples of his school of research, but it must be remembered that he enjoyed no opportunity to teach the young men who were pursuing the higher courses in zoology at Harvard. Through an unfortunate arrangement those who had charge of the various collections in the Museum of Comparative Zoology were not encouraged to give lectures to students, and they worked on throughout the years, their voices silenced, yet with active young minds eager to listen and to learn always near them. Moreover, the spirit of the department of zoology at Harvard during Hyatt's life-time was dominated by Weismannism, and Hyatt's views were thus in disfavor. Upon the rare occasions of his lectures he felt obliged to present not facts—the foundation-stones of his theories—but the theories themselves. Thus the impression grew up that Hyatt was a dreamer and that his theories were based upon erroneous or meager observations. Nothing could have been farther from the truth, for I have myself been surprised, in reading over his publications, to discover that his writings are crowded with accurate observations of indisputable fact, and even if the future should demonstrate that his theoretical deductions are wholly false, he will still be remembered as a great and accurate observer of nature. Concerning the truth or falsity of his so-called acceleration or "old age theory" we are obliged to admit that it has never been disproved even if it be not yet accepted as true. Hyatt's fate may be that of Lamarck and of many another theorizer: Appreciation and respect for his views must come only years after his death.
I will endeavor to give a simple explanation of his theories of evolution, avoiding the complex technical terms which he employed. He believed that the race, like the individual, has only a limited store of vitality and that both must develop, progress, decline and die in obedience to one and the same law. Thus the growth-stages of the individual actually resemble the stages in the evolution of the race to which it belongs; as he puts it, "the cycle of ontogeny is an individual expression and abbreviated recapitulation of the cycle that occurs in the phylogeny of the same stock." "Phylogeny, like ontogeny, is first progressive and thus attains an acme of progress. This acme is followed, however, by a stage of retrogression ending in extinction."
Hyatt derived his ideas of evolution from a study of the fossil nautiloids and ammonoids, those beautiful chambered shells which appear in the Cambrian; and the ammonoid branch of which becomes extinct in the Cretaceous, while to-day the half-dozen species of Nautilus are all that remain of the nautiloids. He was an ardent student of these fossils, and of the 103 titles in the list of his papers, 38 are upon these shells. He proved that the ammonoids are descended from the nautiloids, for he discovered that the protoconch or primitive shell of the nautiloids is soft and composed of flexible conchiolin so that it is