970 THE AMERICAN NATURALIST.  [VOL. XXXIII. 
systems, and it is the phenomena of localization which occur in such 
systems that require an elementary vitalistic force for their explana- 
tion. An organization as regards primary axial relations, which is 
present at the beginning of development, is considered to be an 
essential part of the conditions of every harmonic equipotential 
system, and it is therewith an essential presupposition of its differen- 
tiation. Moreover, the activities which occur in such a system as 
the result of some disturbance of the course of development indicate 
the existence of a regulatory power, which is a fundamental character 
that is intimately associated with the localization of differentiation. 
In defining formally the localizing action which takes place in 
harmonic equipotential systems, Driesch makes first a statement in 
' terms of cause and effect. Thus we may suppose one of the terminal 
points of the axis of any structure under consideration to be the seat 
of forces which act at a distance. This place may be said to exert 
an influence, to which that part upon which it works must be able to 
respond. Reverting to the constriction of the archenteron of the 
gastrula of echinoderms, the author claims that the cause of the 
constrictions lies in the “potency” of the system; the ZFernkraft, 
acting through a definite typical distance, determines where the con- 
strictions shall be. The distance, however, is not absolute, but 
proportionate to the size of the system. As the system becomes 
modified and more complicated, new points of reference are formed, 
from which still other sorts of /érnkraft act. If the formation of 
the mouth of the larva of echinoids be taken as another example, the 
force in question is presumed to operate from the anterior and pos- 
terior poles, and at a certain proportionate distance between them ; 
its localization in the median ventral line depends upon the primary 
bilateral orientation of the whole embryo, which results in the taking 
on of a unique and special character by that line. The writer shows 
furthermore that this localizing force may act not only upon the 
surface of a sphere or other curved surface, but also upon the area 
between two concentric spheres, etc. 
In treating of the relations of the effect (vzz., the action of locali- 
zation) to the cause (the postulated force), Driesch shows that con- 
ditions obtain which are very different from those of purely physical 
or chemical transformations, for the cause is neither transferred 
quantitatively to the effect, as in mechanical and physical action, nor 
does it reappear in the effect as a product of the reaction, as in 
chemical transformations. In the case at hand every specific cause - 
(acting in reference to quantity, 7.e., distance) has a corresponding 
