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 C02- It was not possible to determine positively whether 

 COz 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 C0 2 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. 



