"4. Scraped in rapid succession five equatorial and equidistant injuries--Echinus crawled actively in one determinate direction; the equal and equidistant injuries all round the globe neutralized one another. "5. Scraped a band of uniform width all the way round the equator--same result as in 4. "6. Band of injury in same specimen was then widened in the side facing the direction of crawling--no effect. Still further widened--slight change of direction, and, after a time, persistent crawling away from the widest part of the injured zone. Repeated this experiment on other specimens by scraping round the 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. "7. Scraped on one side of the equator, and, after the animal had been crawling in a direct line from the source of irritation for a few minutes, similarly scraped equator on the opposite side--animal reversed its direction of crawling; it crawled away from the stimulus _supplied latest_. "8. Scraped a number of places on all aspects of the animal indiscriminately--direction of advance uncertain and discontinuous, with a strong tendency to rotation upon vertical axis." These observations show conclusively that the whole external surface, not only of the soft and fleshy Star-fish, but even of the hard and rigid Echinus, is everywhere sensitive to stimulation. Closer observation shows that this sensitiveness, besides being so general, is highly delicate. For if any part of the external surface of an Echinus is lightly touched with the point of a needle, all the feet, spines, and pedicellariæ within reach of that part, and even beyond it, immediately converge and close in upon the needle, grasp it, and hold it fast. This simultaneous movement of such a little forest of prehensile organs is a very beautiful spectacle to witness. In executing it the pedicellariæ are the most active, the spines somewhat slower, and the feet very much slower. The area affected is usually about half a square inch, although the pedicellariæ even far beyond this area may bend over towards the seat of stimulation, which, however, from their small size they are not able to reach.