218 
PACIFIC SCIENCE, Vol. XI, April, 1957 
tonereis costae (Durchon, 1956), but it is not 
known whether or not this fighting reaction 
occurs in these species. 
REPRODUCTION AND DEVELOPMENT 
Sex Ratio 
As reviewed by the author (1954), little is 
known concerning the sex ratio in the nereids. 
A ratio of one to one exists in Nereis grubei 
(Reish, 1954) on the basis of laboratory- 
reared specimens and field collections. Popu- 
lation studies showed a ratio of five males to 
four females in Perinereis nuntia var. hrevicirris 
Grube (Takahasi, 1933), and 40 per cent 
males in Nereis diversicolor from South Baltic 
Sea (Bogucki, 1954) but only 10 per cent 
from the southern English coast (Dales, 
1950). 
Specimens of N. caudata were isolated into 
individual petri dishes shortly after they had 
left the parent tube. These worms were ob- 
served periodically for signs of egg formation. 
Those specimens which did not develop eggs 
were placed separately into a dish containing 
a female. The behavior of these worms was 
observed when they came in contact with one 
another. If the animals did not fight, then the 
unknown was considered a male. If the animals 
did fight, then the unknown was considered 
to be a female. The worms were then re- 
turned to separate petri dishes for further 
observations. No changes in the response to 
the fighting reaction were observed subse- 
quently. A total of 170 specimens were iso- 
lated in this manner; they were offspring from 
six different matings. The results indicated a 
sex ratio of one to one; there were 88 females 
and 82 males. 
Spawning 
Spawning has never been observed in N. 
caudata. It has been described for several spe- 
cies of epitokal nereids (Reish, 1954) and in 
Nereis diversicolor (Bogucki, 1954). In N. 
diversicolor , a non-epitokal form, Bogucki 
found that the eggs are released through rup- 
tures in the body wall, and that sperm may be 
discharged either through the nephridia or 
through ruptures in the body wall. 
Some details concerning spawning behavior 
in N. caudata can be given, however. A series 
of 10 dishes, each containing a male and fe- 
male, were observed at hourly intervals during 
the day (but not the week end) for a three- 
week period. Eight of the ten pairs spawned 
during the period. In one instance the female 
laid all her eggs between one hour observa- 
tional periods. In a second instance a female 
was seen that had laid about one-half of her 
eggs. It is not known whether or not she was 
in the act of laying at the time of observation. 
She died three days later without laying any 
additional eggs. The remaining six pairs laid 
eggs either during the night or over the 
week end. 
Freshly laid eggs of N. caudata were molded 
into a mucoid tube of one egg in thickness 
by the male. The male was undulating its 
body at all times. At first the eggs were free 
and easily withdrawn with a micropipette, but 
after the male had molded them into an egg 
tube, they became appressed and were diffi- 
cult to remove with a micropipette. No gela- 
tinous envelope (Hemplemann, 1911) sur- 
rounded the fertilization membrane as is 
typical for the epitokal nereids. 
No sperm were observed in the water dur- 
ing placement of the eggs by the male. No 
dissections were made of these males. Periodic 
coelomic smears of the posterior part of 
known males did not reveal the presence of 
any bodies that could be definitely attributed 
to sperm or spermatic masses. Sperm was seen 
embedded within the space between the fer- 
tilization membrane and the developing ovum 
by Herpin (1926, fig. 115) and the author. 
Fate of the Parents 
Herpin (1923; 1926) stated that following 
completion of the larval incubation period, 
the male resumed its former life, and in one 
instance a male would reproduce a second 
time. The fate of the female was unknown 
except in one instance where Herpin noted 
