The paddles of Hcsione, the bristle worm, are sup- 

 ported by stiff bristles and trail a long filament, 

 giving a fringelike effect as the animal undulates 

 from side to side. The head ( top ) bears eyes and 

 several pairs of sensory tentacles. (Wimmer) 



reaches sexual maturity during the spring and sum- 

 mer months when the extreme high tides at new 

 moon come near midnight. One after the other the 

 male heteronereids appear at the surface, each a 

 mere V2-inch animal but swimming furiously. Fe- 

 males with red after-segments rise slantwise from the 

 depths and join the crazed ballet. The males redou- 

 ble their pace and commence shedding sperm cells 

 as though they were stunt planes skywriting a mes- 

 sage of welcome. This change in the water excites 

 the female heteronereids, and they release their eggs 

 through rents in the body walls of the loaded seg- 

 ments. By dawn, the survivors are spent. 



On the New England coast, Platynereis megalops 

 swarms for about two hours every night during the 

 dark of the moon in summer months. In this species 

 the male heteronereids appear to be in two parts: an 

 anterior portion swimming violently with the maddest 

 capers, and a posterior portion tagging along like a 

 trailer, loaded with sperm cells. The females attack 

 the males and bite off the segments containing the 

 sperms. This mass the female heteronereid swallows 

 in one long gulp. The sperms emerge into her phar- 

 ynx, penetrate the segments where her eggs are wait- 

 ing, and accomplish fertilization internally. Only af- 

 ter the event is complete will her body wall rupture 

 and spill out the sexual products. Eggs of P. megalops 

 cannot be fertilized artificially in sea water; some es- 

 sential ingredient is missing. 



Most famous of these nocturnal annelid ballets is 

 the swarming of the palolo worm Eunice viridis in 

 the South Pacific. There the big polychaetes live in 

 holes among the coral reefs, hunting for food in the 

 same general way as any Nereis. But at the third 

 quarter of the moon in October and November come 

 the "little rising" and the "great rising" for which the 

 native peoples wait — ready to feast on the swarming 

 worms. 



At this season the palolo is mature, with eggs or 

 sperm concentrated in a hinder part of the body. 

 This posterior portion develops an eyespot and, at the 

 appointed time, separates from the parent to swim 

 to the surface and there mate like a heteronereid 

 with other similarly dissociated individuals. This is 

 actually mating by proxy, for the parent palolos re- 

 main in the rock crannies and develop new reproduc- 

 tive regions for the following year. 



A very different polychaete worm swarms in the 

 darkness near Bermuda. OdontosyUis partners find 

 one another in the black water by bright lumines- 

 cence. The little males flash like fireflies as they swirl 

 near the surface. Each female glows steadily until a 

 male reaches her and mating begins. Then her light 

 goes out permanently, and so does his. 



Nereids are inconspicuous as they prowl the bot- 

 tom and tunnel through its surface sediments. Re- 

 lated worms, with added protection from enemies, 

 can be more conspicuous in their foraging. 



Among coral reefs of the Bahamas and West In- 

 dies, Hermodice caninciilata moves about in appar- 

 ent unconcern over the nearness of hungry fish. Its 

 8-inch body offers an attractive meal, yet few crea- 

 tures molest Hermodice the fire worm. The soft-ap- 

 pearing white bristles on the rose-pink sides may sug- 

 gest the texture of a Persian cat, but they are fine, 

 stiff, brittle lengths of glasslike material that pene- 

 trate skin or the lining of mouth and stomach, pro- 

 ducing agonizing pain. Brushing against Hermodice 

 is like brushing against a hot poker. The burning sen- 

 sation lasts for about an equal length of time, and is 

 only aggravated by rubbing, since this drives the 

 broken bristles even deeper. 



Scale worms carry on their backs shields — over- 

 lapping plates in pairs — as armor. Lepidonotiis has 

 twelve such pairs, Eimoa fifteen, and Halosydna 

 eighteen. These flattened worms, from 1 to 4 inches 

 in length, are found on both sides of the North At- 

 lantic where a beachcomber can discover them. 



An even more astonishing polychaete of these 

 same regions is the sea mouse Aphrodite acideata 

 (Plate 85), whose fifteen pairs of scales are com- 

 pletely hidden by a dense felt of long hairs, grayish 

 down the middle of the rounded back, brilliant iri- 

 descent green and gold along the oval sides. Sea mice 

 reach a length of 7 inches and a width of almost 3, 

 far exceeding in size the mammals for which they 

 were named. 



The polychaetes that move about so freely are of- 

 ten grouped for convenience as "Errantia," the wan- 

 derers. Their counterparts are the more settled 

 worms, the "Sedentaria." The latter build regular 

 tubes and maintain a fixed address. Actually no 

 sharp distinction can be drawn, for many of the 

 wanderers are like Nereis in building mucus-lined 

 tunnels in the bottom. Cistenides, among the sup- 



2021 



