The Habits and Reactions of a Comatulid, Tropiometra Carinata. 115 



inference from the specimens seen is that the young are uniformly 

 yellow^ or brownish-yellow, and that the purple pigment develops as 

 they mature, in some individuals completely obliterating the original 

 color, but usually appearing simply as spots, blotches, and cross-bands. 

 One could scarcely avoid the impression that the development of the 

 pigment is associated with life in the open sunlight, but there was no 

 chance to secure an answer to the interesting question which suggests 

 itself: Do the bright-colored individuals avoid the sun because they 

 lack pigment or do they lack pigment because they have never lived 

 exposed to the sun? 



Several very small individuals were found under rocks on Buccoo 

 Reef, but the smallest one seen (having arms about 18 mm. long) was 

 discovered in a clump of Corallina. The largest specimen measured 

 had an arm-length of nearly 100 mm., and a few specimens exceeded 

 that, but the great majority had arms 60 to 80 nmi. long. No speci- 

 mens with more or fewer than ten arms were noted, in more than 200 

 examined, but several cases of arms forked distally were seen and in 

 one case a forked pinnule was noted. As a rule the arms were approxi- 

 mately equal, but in some individuals those of one side were distinctly 

 shorter than the others. In such cases, however, it was usually obvious 

 that the short arms were regenerating. 



FOOD. 



Although some individuals Uve suspended under rocks with the 

 mouth down, while the great majority are erect with the opening 

 upwards, the character of the food is in all cases planktonic — that is, 

 it does not consist of such organic matter as happens to fall on the 

 disk and arms, but is made up of the living, active plankton. When 

 examined under the microscope, the stomach contents are seen to 

 consist of a mixture of vegetable and animal food, the former pre- 

 dominating. 



The plants are diatoms and unicellular green algse, with occasional 

 fragments of other seaweeds. The condition of the green algse showed 

 that most, if not all, were ingested while living, and the same seemed 

 to be true of the diatoms. Of animals, Crustacea were most frequently 

 noted, but a few foraminifera were also seen. The crustaceans were 

 minute amphipods, copepods, and crab zoseas, and all were in such 

 condition as to leave no doubt that they were alive when ingested. 

 Just how such active animals are actually captured and forced into the 

 mouth is not clear. As compared with the comatulids studied in 

 Torres Strait, Tropiometra shows an unusual proportion of animal food 

 in its diet, but this may of course be purely a local or seasonal matter. 



4n support of A. H. Clark's views on the color of young crinoids. See Geog. Jour. London 

 Dec. 1908, p. 606. 



