The Comatulids of Torres Strait. 121 



CONCLUSIONS. 



In making my deductions from the observations made at Mae'r, I 

 wish to emphasize the fact that other species of crinoids, particularly 

 members of other families, will probably show quite different and no 

 doubt often contradictory reactions. It is also very likely that the 

 same species, studied in a different locality or studied at Mae'r, during 

 the rainy season, would give results in some degree different from those 

 I have secured. Undoubtedly our knowledge of the habits of crinoids 

 as a class, or even of comatulids alone, is altogether too slight to warrant 

 the drawing of any far-reaching conclusions. Because of this con- 

 viction it seems necessary to review Mr. A. H. Clark's paper, already 

 referred to, and point out what seem to be the mistakes he has made 

 apparently from basing his assertions on the study of structure rather 

 than on the observation of living crinoids. 



First, as to the crinoids being, "as a class," "probably the most 

 strictly sessile* of all marine organisms : Many of them are stalked and 

 do not move, and those forms in which the stalk is partially or entirely 

 lost in adult life probably move but very seldom, and not at all unless 

 under strong compulsion" (1908, Geog. Jour., London, p. 602). So far 

 as the stalked forms are concerned there is no little reason for believ- 

 ing that these crinoids are rarely attached and are capable of moving 

 about. As for the unstalked forms, I think my observations at Mae'r 

 show that while it is true they are usually inactive under uniform 

 conditions, they both can and do move, by either swimming or creep- 

 ing. To consider them more "sessile" than corals, sponges, or bar- 

 nacles seems to me absurd. If the reply is made that these groups all 

 have active, free-swimming larval forms, which provide for their wide 

 distribution, the natural answer is that comatulids also have them. 



Mr. Clark says of comatulids: "Their free-swimming larval period 

 (so far as we know) is of short duration; the larva soon sinks to the 

 bottom and becomes fixed." The parenthetical is no doubt the 

 saving clause here, for, excepting the European species of Antedon, 

 there is not a single crinoid of which we know anything whatever about 

 the length or habits of the free-swimming larval period. f Of course, 

 Mr. Clark's opinions in the matter, based on the examination of the 

 eggs of a number of species of comatulids (alcoholic material), may be 

 correct, but better evidence is needed to demonstrate that crinoids 



*This use of the word "sessile" is admitted by the Century Dictionary, but is said to be rare. 

 The idea is apparently not merely "sedentary," but actually "not capable of any extended 

 movement." 



tElsewhere (Proc. U. S. N. M., vol. 38, p. 213; 1910) Mr. Clark, while arguing in defense of a 

 different assumption, says that the species "of Tropiometra have a very wide distribution, necessi- 

 tating a prolonged free-swimming stage; are we justified in saying that the larvae of Tropiometra 

 may not turn out to be plutei or something like them?" If one may argue thus with reference 

 to Tropiometra, why not also with reference to the dozens of other genera concerning which we 

 are equally ignorant? 



