POLYCHAETE WORMS, PART 1 157 



and palps are directed veiitrally and are not visi])le dorsally (fig. 43^) ; 

 body is divided into 2 regions, anterior region with setae similar to 

 atokous form and posterior region tapering gradually, with swimming 

 setae (since the notopodial horaogomph falcigerous setae of the 

 atokous form begins around setiger 20 and are replaced by swimming 

 setae up to the posterior end, they will not usually be found in the 

 heteronereids) . Extra thin flattened lamellae are on the parapodia 

 and bases of the dorsal and ventral cirri. Pygidium with a pair of 

 midventral cirrophores with the anal cirri, or cu'ri may be broken off. 

 Table 1, page 158, shows how the sexually dimorphic males and females 

 differ. 



Biology. — The species, including male and female heteronereids 

 massed with eggs and many small ones, is particularly associated with 

 algal masses (Fucus) and floating seaweed (Sargassum). It is very 

 active in all its motions, swimming rapidly. It forms tenacious, 

 transparent, parchment-like or wealdy chitinized tubes on the algae, 

 in which foreign material, such as sand gi-ains or fragments of bryo- 

 zoans, may be incorporated irregularl3^ It is found in crevices of 

 rocks, on pilings, wharfs, among algae, sponges, and hydroids (as 

 Pennaria). It is dredged in rather shallow waters on shelly bottoms, 

 among br3^ozoan nodules, ascidians and sponge clumps. It feeds on 

 algae. The heteronereids are found at the surface as well as the young 

 of all sizes from 6-8 segments up to 10 mm. or more in length. 



In the Woods Hole region, sexual forms are found at the surface 

 during the summer months from June into September (Bumpus, 

 1898c, Verrill, 1882, Wilson, 1892). According to Just (1914) in 

 the Woods Hole region, they show lunar periodicity, swarming during 

 the dark of the moon during the months of July and August. At 

 Beaufort, North Carolina, they are found in June and July (Hartman, 

 1945). At Naples, they are found swarming from October to May, 

 tending to center around the time of the first and third quarters of 

 the moon (Lillie and Just, 1913). 



The species is noted for its extreme reproductive plasticity. Some 

 of the reports may be due to confusion of species, due to difficulty in 

 detecting distinguishing morphological characters or due to somewhat 

 abnormal conditions. The following have been reported for the 

 species, mostly studied in the Mediterranean (Moquin-Tandon, 1869; 

 Herpin, 1926; Ilaucnschild, 1951): 



A. Epitokous, heteronereid forms, metamorphosing into sexually 

 dimorphic males and females which become pelagic and swarm at 

 the surface; the eggs have relatively less yolk (with few relatively 

 large yolk droplets, eggs under 180 m in diameter, according to 

 Hauenschild, 1951) and develop into planktogenic swimming trocho- 



