856 
MR. G. J. ROMANES AND PROFESSOR J. C. EWART 
not wishing to rely on the uncertain method of employing coloured glass, we were 
unable to ascertain how the Echinoderms might be affected by different rays. 
On removing with a pointed scalpel the eye-spots from a number of Star-fishes and 
Echini without otherwise injuring the animals, the latter no longer crawled towards 
the light, even though this were admitted to the tank in abundance; but they crawded 
promiscuously in all directions. On the other hand, if only one of the five eye-spots 
were left intact, the animals crawled toward the light as before. 
§ III. Section. 
1. Star-ftsh. —Single rays detached from the organism crawl as fast and in as 
determinate a direction as do the entire animals. They also crawl towards the light, 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 themselves as quickly as 
do the unmutilated organisms. 
Removing the tip of a severed ray does not impair any of these movements, except, 
of course, the crawling towards light, which it completely destroys. 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 physiological 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 
ULvided into two parts ; that is to say, the distal half of the row may crawl while the 
proximal half is retracted, or vice-versa, 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 of that line—assume various movements and shapes. The central portion is 
particularly apt to take on the form of an arch, in which the central end of the 
severed ray and the line of nerve-section constitute the points of support (tetanus ?) 
(Plate 83, fig. 27), or the central end may from the first show paralysis, from which it 
never recovers. The distal end, on the other hand, usually continues active, twisting 
about in various directions, and eventually fastening its tip upon the floor of the tank 
to begin the spiral movement of righting itself (Plate 83, fig. 27). This movement 
then continues as far as the line of nerve-injury, where it invariably stops (Plate 83, 
fig. 27). The central portion may then be dragged over into the normal position, or 
may remain permanently inverted, according to the strength of pull exerted by the 
distal portion ; as a rule, it does not itself assist in the righting movement, although 
its feet usually continue protruded and mobile. 
