POLYCHAETE WORMS, PART 1 159 



phores and forming 3-segmented pelagic larvae with long compound 

 setae. Two modifications are: 



(1) A noncopulatory external fertilization, as reported by Just 

 (1929) and others for P. dumerilii at Naples. Around the slowly 

 swimming female, the active males move with ever increasing rapidity 

 and more closely set spirals. The males then discharge their sperm, 

 into which the female discharges her eggs, and then the adults sink to 

 the bottom of the sea. 



(2) A remarkable copulatory mechanism followed by internal 

 fertilization, as described by Just (1914) for Platy nereis megalops in 

 the Woods Hole region (P. megaloj^s seems indistinguishable morpho- 

 logically from the Alediterranean P. dumerilii and has been put into 

 S3aionomy herein, as has been done by others; it may be, however, 

 that the species are distinct; megalojps should probably at least be 

 considered as a subspecies). The small, reddish males appear first, 

 swimming Tvdth great rapidity in an ever narrowing circle while the 

 larger, pale yellow females appear later. As the male comes in the 

 vicinity of the female, he swims very rapidly in spirals, entwining 

 the female. The female receives the anal segments of the male in her 

 jaws, the sperm are swallowed and pass through lesions of the pharynx 

 into the body cavity; the sexual adults separate and the fertilized 

 eggs stream from the posterior segments of the female through lesions 

 of the body wall (about 6 seconds after the female has received the 

 anal segments of the male; previously the body wall of the female has 

 become extremely thin and the digestive tract has become but a rem- 

 nant) ; the female sinks from view and apparently dies. 



B. Atokous nereid form, without metamorphosis; yolky eggs (over 

 250 II in diameter, filled compactly with small yolk globules, according 

 to Ilauenschild, 1951) are deposited in the tube and incubated by the 

 male; nonpelagic neridogenic larvae of three segments leave the egg 

 membranes and creep away. The atokous forms are protandric 

 hermaphrodites, described originally for Nereis massiliensis Aloquin- 

 Tandon, 1869. Thus the following may be found: 



(1) Small greenish "males" filled with ripe sperm and small unripe 

 eggs; 



(2) Larger yellowish females with yolky eggs (the sperm usually 

 disappear by the time the eggs ripen) . 



When "males" are present, the females shed the eggs within the 

 tube where they develop, incubated by the "male" (Herpin, 1926); 

 the female dies sometime after spawning; in the protandi'ic "male," 

 the eggs mature, and it becomes a female. According to Herpin 

 (1926) and others, this is to be considered a reproductive phase of 

 P. dumerilii. According to Hauenschild (1951), P. dumerilii and 

 P, massiliensis should be considered as distinct, the former reprodue- 



