688 BULLETIN 82, UNITED STATES NATIONAL MUSEUM. 



When kept with other animals in an aquarium Antedons are among the 

 first to die, and although Carpenter was at first inclined to attribute this to the 

 circumstance of their habitually living under a much greater pressure of water 

 than the littoral animals with which they are associated in such artificial collec- 

 tions, yet he soon came to be satisfied that the real explanation was to be found 

 in their inability to sustain any deficiency in the purity of the medium they 

 inhabit. For by placing them by themselves in small numbers in an adequate 

 supply of water, and by frequently renewing this, he succeeded in keeping the 

 same specimens for several weeks together, and the deficiency in vigor which 

 they showed at the end of that time, manifested in a general flaccidity of the 

 arms and in a disposition to cast off portions of them, appeared quite explicable 

 by the insufficiency of their food supply, made evident by the progressive shrinking 

 of the visceral mass, the ventral surface of which came at last to be concave 

 instead of protuberant. 



Moreover, it happened on several occasions that if a dozen specimens of 

 Antedon were thrown at night into a large basin of water and were left without 

 any means of attachment they were all found dead in the morning, conglomerated 

 at the bottom of the basin, clinging to each other with their dorsal cirri and having 

 their arms intertwined in such a manner as to suggest the idea that they had died 

 of the asphyxia produced by overcrowding after exhausting themselves in efforts 

 to find a suitable attachment; while if, in a basin of the same size and containing 

 the same quantity of water, there were placed with a like assemblage of specimens 

 a sufficient number of rough stones to afford them all a basis of attachment, they 

 would be all found in the morning in a state of full expansion, with every appear- 

 ance of health and vigor. 



Regarding the comatulids at Mae'r Island, Torres Strait, Dr. H. L. Clark savs 

 that 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 and 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. 



Doctor Carpenter remarked that the intermixture of a small proportion either 

 of fresh water or of glycerine with the sea water in which Antedon Mfida is living 

 is very speedily fatal. 



