THE ANNUAL BREEDING-SWARM OF THE ATLANTIC PALOLO. 
By ALFRED GOLDSBOROUGH MAYER. 
The habits of the “ Atlantic palolo” are quite similar to those of the 
palolo worm of Samoa and the Fiji Islands. The worms are, however, 
specifically different, the Atlantic palolo being Eunice fucata Ehlers, and 
the Pacific worm F. viridis Gray. Moreover, the annual breeding-swarm of 
the Pacific palolo comes upon or near the day of the last quarter of the 
moon in October and November, whereas the Atlantic palolo swarms within 
three days of the day of the last quarter of the moon between June 29 and 
July 28. The annual swarming of the Atlantic palolo has been observed 
only at Tortugas, Florida, and although the worm is abundant in the Baha- 
mas and in other parts of the West Indies, it has not been observed to 
swarm elsewhere than at Tortugas. This may be due to lack of observation, 
but in 1903 I looked for the swarm in Nassau Harbor, Bahamas, on every 
morning between July 10 and 24, inclusive, but no swarm occurred, although 
in the same year, at Tortugas, Florida, Mr. George R. Billbury observed a 
dense swarm on July 17, this being the day of the last quarter of the moon. 
The Atlantic palolo worm lives within crevices in dead, corroded coral, 
or in limestone beach-rock which has become honey-combed by the burrows 
of marine animals. It inhabits only rocks which lie below low-tide level, 
but will live within reefs which are at least 6 fathoms below the surface. 
Large worms are apt to be found only in large coral rocks, and the 
worm is usually coiled backward upon itself, or twisted within its tortuous 
cavity. Mature worms are about 250 mm. long, and the sexual products 
are confined to the 150 posterior segments, which, when swollen by the 
contained eggs or sperm, are thicker than the slender middle part of the 
worm’s body. A mature male worm is represented in natural size in figure I. 
Before sunrise on the morning of the day of the annual breeding- 
swarm, the worm crawls out backwards from its burrow until all of the 
sexual segments and a portion of the slender middle part of its body have 
been protruded. A vigorous helical, corkscrew-like twisting movement then 
comes over the sexual segments. Viewed from the head end of the worm 
this screw-like twisting is in the direction of the movement of the hands of 
a watch. This rolling motion is confined exclusively to the posterior sexual 
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