me intellectually entirely respectable. Of supposed structural life units there is a great variety. Besides the gemmules of Darwin there were the physiological units of Herbert Spencer. Professor Haeckel, the famous German writer, has special structural life units of his own which he terms plastidules; he gave them the charming alliterative title of perigenesis of the plastidules; the rhythm of it must appeal to you all, though the hypothesis had better be forgotten. Then came Nägeli, the great botanist, who spoke of the Idioplasma-Theilchen. Then Weisner, also a botanist, who spoke of the Plassomes. Our own Professor Whitman attributed to his life units certain other essential qualities and called them idiosomes. A German zoologist, Haacke, has called them gemmules. Another German writer, a Leipzig anatomist, Altmann, calls them granuli. Now these different life units, of which I have read you briefly the names, are not identical according to these authors. Everybody else's life units are wrong, falsely conceived, and endued with qualities which they do not combine. There is a curious assemblage here of doxies, and each writer is orthodox and all the others are heterodox; and I find myself viewing them all from the standpoint of my doxy, that of the structural quality of the living matter, and, therefore, interpreting every one of these conceptions as heterodox, not sound doctrine, but something to be rejected, condemned and fought against. These theories of life units have filled up many books. Among the most ardent defenders of the theory of life units is Professor Weismann, whose theories of heredity many of you have heard discussed; though I doubt if many of you, unless you recall what I said previously, are aware of the fact that the essential part of Weismann's doctrine was the discovery of the theory of germinal continuity by Professor Nussbaum, whose name is seldom heard in these discussions. Weismann has gone much farther in the elaboration of the conception of life units than any of the other writers. He thinks the smallest of the life units are biophores. A group of biophores brought together constitutes another order of life units which he calls determinants; the determinants are again grouped and form ids; and the ids are again grouped and form idants. If you want to accept any theory of life units, I advise you to accept that of Weismann, for it offers a large range for the imagination, and has a much more formidable number of terms than any other.
I want to pass now to an utterly different line of study, the question of psychological development. If it be true that the development is most rapid at first, slower later, we should expect to find proof of that rate in the progress of mental development. In other words, we should expect to find that the baby developed faster than the child mentally, that the child developed faster than the young man, and the young man faster than the old. And do you not all instinctively feel immediately that the general assertion is true? In order, however, that
