294 JELLY-FISH, STAR-FISH, AND SEA-URCHINS. 
Section. 
1. Star-fish—Single rays detached from the 
organism crawl as fast and in as determinate a 
direction as do the entire animals. They also 
crawl up perpendicular surfaces, and sometimes 
away from injuries; but they do not invariably, or 
even generally, seek to escape from the latter, as is 
so certain to be the case with entire animals. 
Lastly, when inverted, separated rays right them- 
selves as quickly as do the unmutilated organisms. 
Dividing the nerve in any part of its length has 
the effect, whether or not the ray is detached from 
the animal, of completely destroying all physio- 
logical continuity between the pedicels on either 
side of the line of division. Thus, for instance, if 
the nerve be cut across half-way up its length, the 
row of pedicels is at once physiologically bisected, 
one-half of the row becoming as independent of the 
other half as it would were the whole ray divided 
into two parts: that is to say, the distal half of the 
row may crawl while the proximal half is retracted, 
or vice versd; and if a drop of acid be placed on 
either half, the serial contraction of the pedicels 
in that half stops abruptly at the line of nerve- 
division. As a result of this complete physiological 
severance, when a detached ray so mutilated is 
inverted, it experiences much greater difficulty in 
righting itself than it does before the nerve is 
divided. The line of nerve-injury lies flat upon 
the floor of the tank, while the central and distal 
portions of the ray, i.e. the portions on either side 
