864 
MR. Gr. J. ROMANES AND PROFESSOR J. C. EWART 
and then found no feet wherewith to continue the manoeuvre. The result of this 
experiment was first of all to show us that the Echini invariably chose the unmuti¬ 
lated feet-rows wherewith to right themselves. Probably this is to be explained, 
either by the general principle to which the escape from injury is due,—viz., that 
injury inflicted on one side of an Echinoderm stimulates into increased activity the 
locomotor organs of the opposite side,—or by the consideration that destruction of the 
lower half of a row very probably induces some degree of shock in the remaining half, 
and so leaves the corresponding parts of the unmutilated rows prepotent over the 
mutilated one. Be this as it may, however, we found that the difficulty was easily 
overcome by tilting the animal over upon its mutilated feet-rows sufficiently far to 
prevent the unmutilated rows from reaching the floor of the tank. When held 
steadily in this position for a short time, the mutilated rows established their adhe¬ 
sions, and the Echinus was then left to itself. Under these circumstances an Echinus 
will always continue the manoeuvre along the mutilated feet-rows with which it was 
begun, till the globe reaches the position of resting upon its equator, and therefore 
arrives at the line where the shaved area commences. The animal then remains for 
hours in this position, with a gradual but continuous motion backwards, which appears 
to be due to the successive slipping of the spines—these organs in the righting move¬ 
ments being always used as props for the ambulacral feet to pull against while rearing 
the globe to its equatorial position, and in performing this function on a slate floor the 
spines are liable often to slip. The only other motion exhibited by Echini thus 
situated is that of a slow rolling movement, now to one side and now to another, 
according to the prepotency of the pull exerted by this or that row of ambulacral feet. 
Things continue in this way until the slow backward movement happens to bring the 
animal against some side of the tank, when the uninjured rows of ambulacral feet 
immediately adhere to the surface and rotate the animal upwards or horizontally, 
until it attains the normal position. But if care be taken to prevent contact with 
any side of the tank, the mutilated Echinus will remain propped on its equator for 
days; it never adopts the simple expedient of reversing the action of its mutilated 
feet-rows, so as to bring the globe again upon its ab-oral pole and get its unmutilated 
feet-rows into action. At first sight, therefore, this result seems to point to the con¬ 
clusion that the righting movements are of a merely serial kind ; it seems to indicate 
that the feet are only able to act in one direction, from ab-oral to oral pole, and that 
there is not sufficient central co-ordination to induce them to act hi the opposite 
direction, when it is found to be useless, from the interruption of the series, to con¬ 
tinue the manoeuvre in the ordinary direction. But a little closer thought will show 
that this conclusion is not justified by the facts. For even if we assume that the 
righting movements of the feet are entirely due to some central co-ordinating 
influence, it does not follow, when the execution of these movements is interrupted 
by the highly artificial means of shaving off one-half the feet-rows, that the central 
co-ordinating apparatus should be adapted to meet so unnatural a state of things. 
