Neanthes caudata — Reish 
219 
that the male had eaten the female the day 
following egg-laying. 
The observations of Herpin were con- 
firmed, and the following additional details 
can be given. The female either died after 
egg-laying or was eaten by the male. This 
cannibalistic action by the male is believed 
to be incidental because the fate of the female 
was approximately equally divided between 
the two causes. One female lived a total of 
six days following egg-laying, but this was 
exceptional. Typically the female lives two or 
three days after laying her eggs before dying. 
The females ate Enteromorpha sp. until a day 
before egg-laying, but none of them resumed 
feeding after spawning. 
After the larvae have left the tube of the 
parent, the male may also abandon the tube, 
but not necessarily. The male may reproduce 
and incubate larvae more than once. Many 
males have fertilized and incubated eggs two 
times and one male has successfully incubated 
eggs three times in the laboratory. How soon 
after completion of one incubation period the 
male can reproduce with a second female was 
not completely ascertained because of the lack 
of mature females at the critical time. The 
shortest period of time between two fertiliza- 
tion periods for one male was 27 days. The 
first eggs were fertilized on September 12, 
1954, with all the larvae leaving the tube by 
September 22, 1954. The second female was 
placed with the male on October 4, 1954, 
with fertilization occurring October 8, 1954. 
Neanthes caudata is the only dioecious species 
of nereid known in which at least one of the 
sexes can reproduce a second time. 
Number of Eggs 
Little information on the number of eggs 
or larvae of nereids has been recorded in the 
literature. Smith (1950) stated that Neanthes 
lighti produced several hundred eggs but only 
80 to 100 larvae were released. Rullier (1954) 
found that Micronereis variegata laid from 20 
to 80 eggs in a gelatinous matrix. In Nereis 
grubei the author (unpublished data) found 
the number of eggs to vary from 1,000 to 
49,000. The lower figures were generally for 
those animals reared in the laboratory, and the 
higher figures were from animals collected 
from nature. 
The number of larvae of N. caudata hatch- 
ing from the parent tube were counted rather 
than the eggs because of the greater ease in 
counting. This figure is believed to represent 
a close approximation of the actual number 
of eggs laid by the female since non-develop- 
ing eggs were not seen. Only one count of 
larvae was made from a female collected from 
nature; a total of 481 larvae left the parent 
tube. Counts for seven laboratory-reared fe- 
males ranged from 143 to 791, with a median 
of 365 larvae. 
Fertilization and Early Development 
The unfertilized ovum of Neanthes caudata 
is spherical and yellow (Fig. 1). Eggs from 
laboratory-reared females measured from 420 
to 520 /jl in diameter. The ova observed by 
Herpin (1926) were 600 /jl in diameter, the 
largest size recorded for a nereid egg. No 
distinct cortical layer was observed. 
The process of fertilization has not been 
observed either by Herpin or by the author. 
Eggs that had been laid within an hour al- 
' ' ***** 
Fig. 1. Photomicrograph of an unfertilized egg of 
Neanthes caudata. Diameter, 425 £i. 
