606 BULLETIN 82, UNITED STATES NATIONAL MUSEUM. 



Crinoids dropped beside the live car on reaching the bottom began at once 

 to move away and continued moving, usually in a fairly straight line, until they 

 reached a rock beneath which they could find shelter; but it was not possible to 

 determine their ultimate resting place. 



Professor Semper, who while living in the Philippines kept various species of 

 Comastericlse in his aquaria for weeks together, informed P. H. Carpenter that he 

 never saw the least trace of any irregularity in the alternating movements of their 

 arms when swimming, which would imply that they swam more or less frequently ; 

 and the West Indian Comactinia and Nemaster are said occasionally to swim. 



Doctor Clark also studied the locomotion of Tropiometra picta. at Buccoo 

 Bay, Tobago. He says that, like most of the comatulids hitherto studied, this 

 species is exceedingly sluggish. So far as his observations go, it never swims. 

 Dropped or suspended in deep water, it makes only the most feeble arm move- 

 ments, and unless artificially prevented it sinks rapidly to the bottom. 



When, as a result of some adequate stimulus, it does move, the movement 

 is similar to that of Comanthus; that is, it is accomplished solely by means of the 

 arms, and no particular arms take precedence. In one respect the attitude differs 

 from that of Comanthus, for the body is much more distinctly raised. This is 

 obviously to keep the cirri wholly above the substratum and thus prevent their 

 accidentally catching on it. The movement is always slow and labored and does 

 not continue long. When overturned so that the cirri are uppermost a normal 

 healthy individual invariably rights itself at once, sometimes only very slowly 

 and deliberately but usually without delay. The process is, as in other comatulids, 

 by several arms raising up their side of the body until one or more of them, or 

 some of the neighboring arms, can reach over backwards and secure a hold which 

 will enable them to pull the body over. The cirri play no part whatever in this 

 process, any more than in actual locomotion; they are very inert, move slowly 

 and slightly, and are used only as organs of attachment, a purpose which they 

 serve admirably. The pinnules, even near the tip of the arm, have only weakly 

 hooked tips and are but slightly viscid, and it is consequently difficult for the 

 animal to move or even to right itself except on a rough and rather firm surface. 

 No individuals were seen moving about under normal conditions, but when 

 placed on a bare sandy bottom they crept steadily to its margin of coralline algse. 

 Many specimens were planted on the reef flat near the laboratory, and most of 

 these ultimately disappeared, but whether they crept away or were carried off by 

 tidal movements it is impossible to say. 



On two occasions during the cruise of the Siboga in the East Indies the 10- 

 armed young of Comanthus parvicirra were captured at the surface once at the 

 anchorage off North Ubian, and once in a plankton haul on the south side of the 

 pearl bank in the Sulu Archipelago. It would appear, therefore, that in this 

 species, as apparently in all comatulids, the young are much more active than the 

 adults, and also that the 10-armed young of multibrachiate types are as good swim- 

 mers as the young of the normally 10-armed Antedoninae. 



