390 
R. P. COWLES 
although Ophiocoma echinata and Ophiura appressa were fre- 
quently experimented with for comparison. 
In order to keep the brittle-stars in the best condition possible 
for work in the laboratory, they were placed in large open '^live 
cars," in which were pieces of coral and rock to afford them shel- 
ter. These ^^live cars" were floated in the open sea and were so 
arranged that there was a constant circulation of pure sea-water. 
Ophiuroids are extremely sensitive to impure water and they soon 
show the effects of the same, so care was taken when working 
with them to change the water frequently in order to prevent 
any unusual behavior. 
LOCOMOTION 
There seems to be a very general agreement, either definitely 
stated or implied, that in the case of ophiuroids no one ray has a 
greater functional value in locomotion than another, although, so 
far as I know, no careful statistical study has been made. Preyer 
(1886-1887), Grave (1900), Glaser (1907), Bohn (1908.)2 
In other words, it seems probable that a normal ophiuroid may 
use any ray or interradius as a director, and apparently in the 
long run does not use one ray or interradius more than another. 
There are times, however, during experiments and even under 
natural conditions when an ophiuroid may use a certain ray or 
interradius as director exclusively. This behavior can usually 
be traced to the lasting effect of some previous stimulus, such as 
contact with a more or less vertical surface or to some stimulus 
such as difference in light intensity. 
TUBE-FEET AS LOCOMOTOR ORGANS 
The statement that the ambulacral appendages of the ophiu- 
roids do not act as locomotor organs can no longer be accepted 
since the studies of Grave (1900) on Ophiura brevispina and von 
Hj. Ostergren (1904) on Ophiocoma nigra. 
2 Bohn, however, finds that sometimes large specimens of the starfish, Asterias 
- rubens, show "une sorte de preference pour certain bras" (p. 29); Cole (1910), as 
a result of his statistical study of the locomotion of the starfish, finds that there 
is a tendency to use certain rays more than others. 
