262 THE BIOLOGY OF THE SEASONS 



part becoming dilated and embellished, so that the animal 

 as some one has put it, is like a caterpillar in front and like a 

 butterfly behind. In many species, especially in the family 

 of Syllids, part of the body, laden with germ-cells, is set adrift 

 at the breeding-season, and, after swimming about for a while, 

 breaks up in the waters. This is what happens with the 

 palolo. 



For the strangest feature of the palolo-swarm is not in 

 the enormous numbers since the shore abounds in prolific 

 animals ; nor in the regularity of occurrence since Nature is 

 full of these subtle rhythms ; nor in the fact that these 

 burrowers among the coral should be swimming in open 

 water, in a pelagic agony rather than a pelagic existence 

 (as Professor M'Intosh puts it) since many shore-animals 

 have a pelagic or semi-pelagic phase in their life-history ; but 

 surely this, that all these writhing worms are headless. In 

 the most literal sense, they have all lost their heads ; they 

 are not worms, but parts of worms the detached posterior 

 portions laden with germ-cells. 



The story of the Pacific palolo is so extraordinarily 

 diagrammatic that no apology is needed for re-emphasising 

 its biological significance by noticing what happens with its 

 congener at Tortugas, Florida, Eunice fucata, the " Atlantic 

 palolo/' Dr. Alfred G. Mayer, who has made a great stride 

 by his studies in the intimate physiology of jelly-fishes, has 

 given a fine sketch of the annual event. 



" 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 

 E. 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 



