854 
MR, G. J. ROMANES AND PROFESSOR J. C. EWART 
“ 7. Scraped similarly near pole, and half-way between pole and equator—little or 
no effect. 
“ 8. Scraped in rapid succession five equatorial injuries, one on each of the five inter- 
ambulacral spaces— Echinus crawled actively in one determinate direction; 
the equal and equidistant injuries all round the animal neutralized each other. 
“ 9. Scraped a band of uniform width all the way round the equator—same result 
as in 8. 
“ 10. Band of injury in 9 widened on the side facing direction of advance—no 
effect. Still further widened—slight change of direction, and, after a little 
time, persistent crawling away from widest part of injured zone. 
Repeated experiment on other specimens, scraping round whole equator and 
simultaneously making one part of the zone of injury wider than the rest— 
same result; the animal crawled away from the greatest amount of injury. 
“11. Scraped on base side of equator facing direction of advance—immediate 
reversal of that direction. 
“ 12. After a few minutes similarly scraped opposite side—direction of advance 
immediately reversed to original one. 
“ 13. Similarly scraped midway between the two previous injuries—direction of 
advance became oblique between the two first injuries, with a considerable 
simultaneous rotation upon the vertical axis of the animal. 
“ 14. Similarly scraped a number of places on all aspects of the animal indiscrimi¬ 
nately—direction of advance became uncertain and discontinuous, with a 
strong tendency to rotation upon vertical axis.” 
5. Physiology of the Pedicels. —Taking here the Star-fish as a type of the 
Echinodermata, the results of our experiments on this head, and so far as stimulation is 
concerned, are as follows. When a drop of acid, or other severe stimulation is applied 
to any part of a row of protruded pedicels, that whole row is immediately retracted, 
the pedicels retracting successively from the seat of irritation—so that if the latter 
be in the middle point of the series, two series of retractions are started, proceeding in 
opposite directions simultaneously; the rate at which they travel is rather slow. This 
process of retraction, however, although so complete within the ray irritated, does not 
extend to the other rays. But if the stimulus be applied to the centre of the disc,, 
upon the oral surface of the animal, all the feet in all the rays are more or less retracted 
—the process of retraction radiating serially from the centre of stimulation. The 
influence of the stimulus, however, diminishes perceptibly with the distance from the 
centre; thus, if weak acid be used as the irritant, it is only the feet near the bases of 
the rays that are retracted ; and even if very strong acid be so used, it is only the 
feet as far as one-half or two-thirds of the way up the rays that are fully retracted— 
the remainder only having their activity impaired, while those near the tip may not be 
affected at all. If the drop of acid be placed on the dorsal, instead of the ventral 
