POLYCHAETE WORMS, PART 1 175 



lower group of neurosetae heterogomph spinigers and falcigers. 

 Parapodia from middle of bod}^ with lips of neiiropodial setigerous 

 lobe subeqiial in length, not extending beyond the aciculum. 



In the posterior parapodia, the middle or presetal notopodial ligule 

 is small or absent. The setae are similar to the more anterior seg- 

 ments except that in the upper group of neurosetae, there are homo- 

 gomph spinigers and few (1-3) heavy, specialized falcigers with end- 

 pieces completely or partially fused to the shafts (fig. 44A). Acicula 

 dark to black. Dorsal and ventral cirri shorter than the ligules. 

 Proboscis with brown amber-colored jaws, each with 5-8 teeth; with 

 amber-colored paragnaths: Area i with 0-9 denticles; areas ii and iv, 

 arched groups; area iii, transverse mass of 2-3 irregular rows; area 

 V, 0; area vi, 1-9; areas vii-viii, wide scattered band of 1-2 UTegular 

 rows. 



Color, in life: very variable, as indicated by its specific name, 

 greenish, yellowish, yellowish green, orange red, reddish brown, with 

 2 darker longitudinal bands; ma}^ have yellowish pigment on prosto- 

 mium; colorless preserved, except for 2 faint to distinct longitudinal 

 bands in the anterior region. Dales and Kennedy (1954) found that 

 the variable color is due to variations in the proportion of green, 

 orange, and brown pigments and that the green pigment is due to 

 biliverdin in minute granules in the epithelial cells under the cuticle, 

 mainly along the borders of the blood capillaries, formed by the 

 breakdown of hemoglobin of the blood. The yellow, brown, and 

 orange pigments were mainly carotenoids. They found that the 

 entirely green form consisted of ripe males (bright grass green), ripe 

 females (darker green), and spawned females. As the worms mature, 

 the tissues undergo phagocytosis, the muscles of the body wall are 

 eroded away, and the amount of hemoglobin diminishes; the biliverdin 

 is derived from the hemoglobin. The females are more variable in 

 color — gi"een with orange or brown pigments. When they spawn, 

 they lose the orange and brown pigments and become uniformly 

 green. Heteronereis stage is lacking. They may be found filled with 

 rather large 3^olky eggs. 



Biology. — -Nereis diversicolor is almost entirely restricted to the 

 littoral zone. It is one of the commonest of all shore polychaetes in 

 the British Isles and northwestern Europe. It is highly euryhaline, 

 easily adapting itself to salt water in the littoral region, to brackish 

 water, and to salt swamps of varying salinites. In the coastal areas, 

 it is especially common where there is a large admixture of fresh 

 water. Smith (1955a-c, 1956) found that when in an essentially 

 "marine-dominated" environment, A^. diversicolor finds its optimum 

 in local, relatively brackish zones; that the bracldsh intertidal water 



