THE SIGNIFICANCE OF PALOLO 263 



last quarter of the moon between 2gth June and 28th 



July." 



The Atlantic palolo worms live within the crevices of 

 coral rock below the low-tide level. When mature they 

 are about 10 in. long and like thick string in girth. 

 Before sunrise on the morning of the day of the annual 

 breeding-swarm, the worm crawls out backwards from its 

 burrow and protrudes the sexual segments, which exhibit 

 a screw-like twisting and break off at a particular point. 

 " On being set free, they swim vertically upward to the 

 surface, where the posterior end of the worm continues 

 to progress rapidly along, moving backward." 



The male " ends " are salmon red or dull pink ; the 

 female " ends " are greenish-grey or drab the sex-contrast 

 eking itself out in colour. If an end be cut, each piece 

 continues to swim backward with its characteristic rolling 

 movement. Normally each worm if we can call it a worm 

 pursues its own course, " without regard to its fellows of 

 either sex" ; and they may be so abundant " that hardly 

 a square foot of the surface above the coral reefs at Tortugas 

 was free of a worm." 



" When the sun is about to rise, and the first faint rays 

 of light fall over the ocean, the worms begin to contract 

 violently, so that the sexual products are cast out through 

 rents and tears in the dermo-muscular wall, and the torn 

 and shrivelled cuticula sinks down to die upon the bottom. 

 Light is not the sole, but only a contributory, cause of this 

 muscular spasm of contraction. . . . Any mechanical 

 shock will bring about an instant bursting of the worm, 

 the females being far more sensitive than the males." 



" After casting off its posterior sexual segments, the 

 anterior part of the worm crawls back into its burrow and 

 regenerates a new sexual end. Only the mature worms cast 

 off their posterior ends ; the immature worms take no part 



