The Habits and Reactions of a Comatulid, Tropiometra Carinata. 117 



was fresh from Buccoo Bay, if placed in a shaded area it remained 

 there; if placed in the sun close to a shaded area, it moved into the 

 shade, but if the board were then removed, it made no effort to move 

 out of the sun ; if placed in the sun some inches from shade, it remained 

 quietly in the light. Generally the individuals were placed upside 

 down in the tank, so that the process of righting might serve to initiate 

 movement. But although they righted themselves promptly, they 

 rarely wandered more than a few inches thereafter. If placed in the 

 tank right side up, they were usually content to remain where put, 

 regardless of whether it was in sun or shade. 



Experiments were made particularly to see whether the brightly col- 

 ored specimens from under rocks reacted differently from the dark 

 individuals from Buccoo Bay, but no constant differences could be 

 detected. Brightly colored examples of Tropiometra seemed to be a 

 little less hardy and became sluggish and inert in the tank more quickly 

 than the dark ones, but the difference was not striking. The final 

 conclusion reached, as a result of all the experiments and observations, 

 is that Tropiometra at Tobago is slightly negatively phototactic, but that 

 other factors in the environment in Buccoo Bay neutralize this tendency 

 almost or quite completely, while on Buccoo Reef it is for some reason 

 strengthened. 



REACTIONS TO TEMPERATURE. 



AMiile it was not feasible to produce really low temperatures, water 

 in the tank fell to 22° C. during the night. At this temperature 

 Tropiometra showed no signs of discomfort or stimulation. When the 

 water was gradually raised to 33° or 34°, responses to mechanical 

 stimulation were normal. At 35.5° two of the four specimens tested 

 were quite unresponsive, but the other two gave normal responses by 

 arm-movements. One continued to respond at 36.5°, but at 37.5° 

 was inert. After a few moments at that temperature the four speci- 

 mens were placed in normal sea- water at 28°, but none recovered. 

 Individuals taken from water at 28° and placed in that at 33° con- 

 tinued to give responses with the arms. At 34°, however, the arms 

 were quiescent, but the pinnules responded. Complete recovery of 

 these specimens resulted when after a few moments they were again 

 placed in water at 28°. Individuals placed in water at 36° gave no 

 responses and failed to recover; they became quite rigid. These 

 experiments show that as compared with the comatulids of Torres 

 Strait, Tropiometra has a surprisingly large temperature range. This 

 is quite in keeping with their habitat in Buccoo Bay, for while the water 

 there probably never falls below 22° C, there is no doubt that at the 

 lowest tides it rises in the shallows to 32° and possibly to 34°. Even 

 should it on rare occasions exceed this figure for a short time, it is 

 evident that Tropiometra would easily survive. Owing to the comat- 



