388 
R. P. COWLES 
The beautiful coordination in the movements of the parts of 
the starfish has always been a subject which has occupied the 
minds of those who have observed the movements of echinoderms ; 
we find nearly all who have studied the reactions of the starfish 
or sea-urchin offering observations, experiments and hypotheses 
to explain the harmonious working of the tube-feet. If one turns 
a starfish over so that it lies with its oral side uppermost for a 
longer or shorter time, the tube-feet wave about in an uncoordi- 
nated manner, but finally a time is reached when one sees a defi- 
nite tendency for the tube-feet to move together seemingly in the 
interest of righting the animal What is it that governs this sud- 
den organized movement? To Preyer the phenomenon seems to 
be regulated by the nerve ring which acts as a centre; similarly, 
Romanes and Ewart recognized a coordinating centre as in part 
responsible for the action; vonUexkiill, who seems to find no co- 
ordinating centre in the sea-urchin, considers coordination in the 
latter to be due to the action of one part on another; Loeb rules 
out the central nerve ring and also even ganglia as coordination 
centres, and judging from his work on the Medusae would prob- 
ably consider the coordination as due to the simple facts of irrita- 
bility and conductivity of the colloidal substances of the tissues, 
thus making the problem one of physical chemistry; to Jennings 
it is a physiological problem based on individual history and racial 
development; and finally to the vitalists the problem deals with 
a determining factor which is non-mechanical. We still seem to be 
as far from the solution as were Romanes, Ewart and Preyer. 
During the last few years there has been much work done on the 
study of the reactions of the lower forms to photic, chemical, 
mechanical and electrical stimuli. Most investigators have paid 
especial attention and have laid especial stress on the uniformity 
in the response to a given stimulus. Jennings, however, both in 
his work on the lower organisms and also in his study of the star- 
fish, has placed in the foreground the somewhat neglected idea 
that there is much variability in the reactions of organisms to a 
given stimulus ; that differences in physiological states often cause 
differences in the reaction to this given stimulus. However, all 
who have studied the echinoderms have recognized the variabil- 
