382 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1911. 
nism of the cell), or, on the other, to the ancient conception of Avital 
element, alien to the province of ie physicist. 
No small number of theories or hypotheses, that seemed for a time 
to have been established on ground as firm as that on which we tread, 
have been reopened in our day. The adequacy of natural selection 
to explain the whole of organic evolution has been assailed on many 
sides; the old fundamental subject of embryological debate between 
the evolutionists or preformationists (of the school of Malpighi, Haller, 
and Bonnet) and the advocates of epigenesis (the followers of Aris- 
totle, of Harvey, of Caspar Fr. Wolff, and of Von Baer) is now 
discussed again, in altered language, but as a pressing question of the 
hour; the very foundations of the cell theory have been scrutinized, 
to decide, for instance, whether the segmented ovum, or even the 
complete organism, be a colony of quasi independent cells or a living 
unit in which cell differentiation is little more than a superficial 
phenomenon; the whole meaning, bearing, and philosophy of evolu- 
tion has been discussed by Bergson, on a plane to which neither 
Darwin nor Spencer ever attained; and the hypothesis of a vital 
principle, or vital element, that had lain in the background for near 
a hundred years, has come into men’s mouths as a very real and urgent 
question, the greatest question for the biologist of all. 
In all ages the mystery of organic form, the mystery of growth 
and reproduction, the mystery of thought and consciousness, the 
whole mystery of the complex phenomena of life, have seemed to the 
vast majority of men to call for description and explanation in terms 
alien to the language which we apply to inanimate things; though at 
all times there have been a few who sought, with the materialism of 
Democritus, Lucretius, or Giordano Bruno, to attribute most, or even 
all, of these phenomena to the category of physical causation. 
For the first scientific exposition of vitalism we must go back to 
Aristotle, and to his doctrine of the three parts of the tripartite soul; 
according to which doctrine, in Milton’s language, created things “‘by 
gradual change sublimed, to vital spirits aspire, to animal, to intel- 
lectual.”” The first and lowest of these three, the guyz} i Opexcenn, 
by whose agency nutrition is effected, is ) zewrn guyz}, the Imsepa- 
rable concomitant of life itself. It is inherent in the plant as well as 
in the animal, and in the Linnewan aphorism, vegetabilia crescunt et 
vivunt, its existence is admitted in a word. Under other aspects it 
is all but identical with the guy) adéqtex) and yeqtex), the soul of 
erowth and of reproduction; and in this composite sense it is no other 
than Driesch’s ‘‘Entelechy,” the hypothetic natural agency that pre- 
sides over the form and formation of the body. Just as Driesch’s 
psychoid or psychoids, which are the basis of instinctive phenomena, 
of sensation, instinct, thought, reason, and all that directs that body 
