NOTES. 175 
NOTES. 
Note on Halodeima atra (Holothuria atra)—During a visit 
to Galle in April, 1915, Mr. A. C. Hayley drew my attention 
to the presence of a worm living upon Halodeima atra, which is 
abundant on the reefs fringing the Fort at Galle. Mr. Hayley 
accompanied me to that part of the reef which lies between 
the lighthouse and the Triton Bastion, where some months 
earlier he had found Halodeima atra in abundance. On this 
occasion, however, we found no specimens. A few were 
discovered on the north-west side of the Triton Bastion, but 
the best locality was at the base of the Aolus Bastion. 
Incidentally I have suggested to Mr. Hayley that it would be 
of interest to determine the seasonal movements of this species 
on the reefs at Galle. Many Holothurians were examined by 
Mr. Hayley and myself, and about 30 per cent. of the specimens 
bore a Polynoid worm. Asarule not more than one worm was 
found ona Holothurian. The presence of the worm was difficult 
to detect owing to its colour adaptation. The colour of the 
general surface of the Holothurian was black or a deep brown, 
and the worm was black with a few insignificant white spots. 
If the worm were detached from its host it very quickly 
returned. Mr. Hayley stated from previous experience that 
the worm died very quickly if it were prevented from 
returning to its host, but I was unable to verify this. The 
identity of the Polynoid worm has not yet been determined. 
Mr. Hayley also drew my attention to another case of 
commensalism in connection with the same Holothurian. 
A small crab was found on a few occasions in the cloacal 
cavity, and in one case in the intertentacular cavity formed 
by the partial withdrawal of the tentacles. This crab also 
exhibited cryptic colouring. The background was black, 
broken here and there by a few yellowish-white lines or spots. 
The crab has not yet been identified. 
Most of the Holothurians were found living on sand, and 
in many cases the back (bivium) was covered with a thin 
coating of sand-grains fastened together by mucus from the 
epidermal cells. There were generally about seven pairs of 
