The Comatulids of Torres Strait. Ill 



succession. That is, supposing the individual had 40 arms, the first 

 stroke would be given by arms 1, 9, 17, 25, and 33, followed almost 

 immediately by 2, 10, 18, 26, and 34, then 3, 11, 19, 27, and 35, and 

 so on until the eight sets had been used, when the first set would come 

 into action again. Not so great a part of each arm is used as in the 

 ten-armed species and the stroke does not carry the arm so far back, 

 but the movements are so rapid and the similarity of the arms to each 

 other is so confusing that it is almost impossible to feel sure that one 

 has made no mistake in the analysis of the method of progression. 

 While the swimming is perhaps just as graceful as that of the ten- 

 armed species, when contrasted with their movement, it is reminiscent 

 of " dog-paddle" swimming as compared with the usual stroke. No 

 satisfactory data were secured regarding the speed of, or distance 

 covered by, the multibrachiate species. 



The creeping movements of the Comasteridse are neither so graceful 

 nor so well coordinated as the swimming movements just discussed. 

 These comasterids usually live in the open spaces among branching 

 corals or on the lower side of large fragments of rock or coral, with 

 their arms extended and floating listlessly in the water. More or 

 less constantly but irregularly the arms bend inward toward the mouth, 

 the tips just brushing the disk and the arm-bases. While these move- 

 ments may be connected with feeding, it was not possible to determine 

 what the connection is. One may perhaps hazard the guess that they 

 keep the ciliated grooves from becoming clogged up. If the coral is 

 broken away or the rock fragment turned over, so that the comatulid 

 is exposed, the animal begins at once to move. In the species with 

 well-developed cirri, notably in Tropiometra afra Hartlaub, the position 

 is maintained by means of them, but they apparently do not play any 

 important part in locomotion. One might suppose that they would 

 be of some use either in pulling or pushing, but there never was the 

 least indication of movement on the part of the cirri in any of the 

 species observed. In the species in which cirri are feebly developed 

 or quite wanting, the position is maintained by the use of some of the 

 arms. It seemed to be usually the shorter arms that were so used, but 

 under laboratory conditions none of the arms remained still for a long 

 period, and while it would seem quite likely that the shorter arms are 

 constantly used as anchors, evidence on the point is not satisfactory. 



Creeping is a rather complex movement, a combined pulling and 

 pushing. Certain arms, usually three or four but sometimes as many 

 as seven, are stretched out to their full extent and the pinnules of the 

 terminal portion catch hold of any available projections. This attach- 

 ment is not only by the use of the minute hooks which are found at 

 the tips of the pinnules, but by the remarkably viscid nature of the 

 secretion from the glands in their epithelium. The degree of viscidity 

 varies in the different species and more or less in individuals. It is least 



