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Color and Size

individuals, arms, seen, specimens and yellow


The first specimens of Tropiometra seen appeared to be uniformly dark purple, purplish-brown, reddish-brown, or bright brown, but a closer examination showed that uniform coloring was very rare. Almost always a longitudinal dorsal stripe on each arm, or transverse bands of more or less width, or both, are present. The color of these markings is yellow of some shade, often dull and bully, but not rarely quite bright. In some individuals the pinnules are also cross-banded with yellow, and the distal pinnules may be uniformly brownish yellow. The cirri are yellow brown, at least dorsally, but are often more or less dusky or purplish on the oral surface; in nearly all individuals, how ever, both young and old, the terminal two or three segments (except the claw) have a dusky spot on the oral side. This marking seems to be a very constant character in Tobagoan specimens. Occasional individuals are found in which the pinnules and dorsal side of the arms are plenteously besprinkled with silvery-white, giving them an excep tionally handsome appearance.

All of the small specimens found were brownish-yellow or bright brown, more or less marked and banded with purple, and this general coloration is not rare in adults, particularly in those found under slabs of rock on Buccoo Reef and in similar shaded places. Some of these individuals were very handsome in their brilliant array of purple and gold, and it was hard to believe they were really identical with the dull-colored specimens from the shallows of Buccoo Bay. A natural 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 mm. 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.


Although some individuals live 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 algae, with occasional fragments of other seaweeds. The condition of the green alga 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 zofeas, 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, Trcrpiometra shows an unusual proportion of animal food in its diet, but this may of course be purely a local or seasonal matter.