The Comatulids of Torres Strait. 119 
with each other and with the cirri dorsally, but sometimes shut up 
together over the mouth. 
Owing, however, to the fact that almost without exception the first 
response is the contraction of the dorsal muscles, it is very easy to 
prepare perfectly expanded specimens. They are lifted from the sea- 
water with the cirri down and plunged abruptly into strong alcohol 
in a shallow flat dish, care being taken to press the disk down at once 
to the bottom of the dish. The contraction of the dorsal muscles 
causes the arms to lie out flat against the dish-bottom. The following 
contraction of the oral muscles is occasionally strong enough to bring 
the arms up over the disk and get them badly entangled, but in the 
very great majority of cases it is so feeble and so quickly followed by 
relaxation that a little manipulation of the arms, smoothing them 
down with the fingers and pressing out the curves, results in perfectly 
expanded specimens. Only in relatively few cases, and these were 
individuals which had been in the laboratory for some hours, was the 
muscular contraction great enough to break off the arm or even cause 
loss of cirri. These cases are, probably to be explained by the suscep- 
tibility of these comatulids to non-aerated sea-water—that is, presum- 
ably, to CO.. It was not possible to determine positively whether 
CQO. was the deleterious substance or not, but there is good reason 
for that belief, because the comatulids were found only on those parts 
of the reef where the aeration of the sea-water was very well provided 
by the surf. However, whether CO, was the factor directly respon- 
sible or not, it is beyond question that the comatulids brought to the 
laboratory were very susceptible to the impurity of the sea-water after 
a few hours in the aquaria. 
If a number of specimens were left in a basin, even with a relatively 
large amount of sea-water, they gradually became inactive and after a 
time perfectly still and made no response to mechanical stimuli. That 
they were not dead was indicated by response to chemical stimuli 
(alcohol, formalin). But if left undisturbed, the arms began to break 
to pieces distally, the process continuing centripetally until only the 
basal parts of the arms were left attached to the disk. Even then 
response to stimuli could be induced if the specimens were placed in 
perfectly fresh sea-water. If, however, they were left undisturbed, 
fragmentation continued until even the basal parts of the arms were 
completely disintegrated. 
There is great individual difference as to the time when amputation 
of the disk from the calyx takes place. It was very common to have 
this happen as the first step in disintegration, but in some individuals 
it was one of the last. Not rarely comatulids shed their disk when 
first taken from the sea and placed in the pail, but such specimens 
lived in the live-car as well, apparently, as those in which the disk 
and digestive system were intact. Presumably regeneration would 
take place under normal conditions as it does in the antedons of 
European seas. 
