OF MYR1APODA AND MACROUROUS ARACHN1DA. 
267 
slightest voluntary or reflex action could be excited in it by any means. But the 
middle division of the same individual was readily excited to reflex actions of the 
legs, and contractions of the segments, by compression of the segments, by irritation 
of the cord with a needle, and by brisk currents of air from a blowpipe. These re- 
flected actions were much stronger in the third or posterior division of the segments, 
and were all induced by similar means. After twelve hours they were feebler in the 
middle division of the segments, but were even more readily excited in the posterior. 
After eighteen hours they were scarcely perceptible in the middle division on the 
application of the needle, and not at all on compression; but they were still easily 
induced in the posterior, and continued to be so in the four or five posterior pair of 
legs, even at the expiration of twenty-four hours. The temperature during the interval 
was not higher than 64° Fahr. 
Experiment 5. — The cord alone was divided in the fourteenth and also the twentieth 
segment, and the intervening portion was destroyed by breaking it down with a 
needle. The animal exhibited in the anterior part of its body all the evidences of 
perfect volition. It moved actively along, turning itself back on either side repeatedly, 
as if to examine the anterior wounded portion, which it felt again and again with its 
antennae, and when attempting to escape, frequently turned back as if in pain and 
aware of some hindrance to its movements, but it seemed perfectly unconscious of 
the existence of the posterior part of its body, behind the first incision. In those seg- 
ments in which the cord was destroyed, the legs were motionless, while those of the 
posterior division, behind the second incision, were in constant, but involuntary 
motion, the movements being similar to those of walking or running, uniformly con- 
tinued, but without any consentaneous action with those of the anterior part, by which 
locomotion was performed, dragging the posterior divisions of the body after them. 
When the animal was held by the posterior segments, reflex actions were excited in 
the legs, and powerful contractions and gyrations of the whole animal were performed 
in those segments; but these movements appeared to be entirely the result of reflex 
actions of the muscles, since exactly similar ones took place in the whole body in 
decapitated specimens. At the expiration of twelve hours the most perfectly volun- 
tary acts were performed by the head and anterior division of the body, such as loco- 
motion forwards or to either side, avoidance of any obstacle, touching it with the 
antennae, which were in rapid action as in an uninjured animal, and attempting to 
reach and to climb up an object presented to it, but not in immediate contact with it. 
But reflex movements alone existed in the posterior division, in which the legs were 
very slowly moved, even when the animal was not progressing. Brisk actions were 
now more easily excited in them than at first, either by contact with the segments, by 
irritation of one or two of the legs themselves, or by a sudden current ot air. By 
these means, when the animal was lying still, actions were immediately excited in all 
the legs of the posterior part of the body anterior and posterior to those which were 
irritated, and these actions were induced in those of both sides of the body, but ap- 
2 N 
WDCCCXLIII. 
