164 U.S. NATIONAL MUSEUM BULLETIN 227 



as the length of the segment (August 22, 1950, Lackeys Bay, Nona- 

 messet Island, Massachusetts). Herpin (1926), in studying the re- 

 productive habits of the species in the English Channel (Cherbourg, 

 France), found that the eggs are of quite unusual size, at maturity 

 reaching a diameter of 600 ^ and filled with abundant yellow yolk in 

 the form of globules of quite small diameter; the sperm are extremely 

 scanty and of quite aberrant form. 



Spawning is preceded by a long period of at least 4 months of couple 

 formation (beginning at the first of May in Cherbourg). This period 

 is associated with a fighting reaction: a female will fight off other fe- 

 males but is attracted to a male; the males will fight oft" any males and, 

 while incubating the eggs, any females; the proboscis is everted and the 

 jaws extend to grasp the opposing animal. A male and female con- 

 struct a single cylindrical tube provided with numerous openings, 

 staying side by side and separating only rarely. The eggs are laid 

 and fertilized in the tube, after which the female leaves the tube and 

 apparently dies after a short time. Keish (1957) found that the fe- 

 males either died 2-3 days after egg laying or were eaten by the males. 

 The male remains and incubates the eggs by executing continual 

 regular undulatory movements, assuring the renewal of water over the 

 eggs. The fertilized eggs adhere to one another and to the wall of the 

 tube, the male having arranged the eggs with his proboscis. Freshly 

 laid eggs were molded into a mucoid tube of one egg in thickness by 

 the male, according to Reish ; the males may resume their former fife 

 and may reproduce and incubate larvae more than once. 



The early development has been followed by Herpin (1926, Cher- 

 bourg, France) and by Reish (1957, southern California). They 

 found that it develops into a nonciliated embryo, which is unique 

 among the nereids. Herpin found that the larvae hatch from the 

 fertihzation membrane after about 11 days (7 days, according to 

 Reish) as a hemispherical larva possessing 3 setigers, with anal cirri, 

 with a mouth but no jaws, and with a large amount of yolk globules. 

 The larvae develop rapidly and, after 30 days (about 21 days, accord- 

 ing to Reish), may possess 20 pairs (17-19 pau-s, according to Reish) 

 of parapodia, the reserves being exhausted; they differ from the adult 

 only by the absence of the fourth pair of tentacular cirri. The larvae 

 leave the tube only after the disappearance of the reserves and at a 

 very advanced stage, thus compensating for the small number of eggs. 

 Reish found 143 to 791 larvae per parent tube. They construct 

 mucoid tubes and begin to feed, there being no true planktonic stage. 

 Development is effected in a single year (Reish found that sexual 

 maturity was reached in 2 months and that 5 generations completed 

 their fife cycle in the laboratory within a period of 1 year). 



