Neanthes caudata — Reish 
225 
Fig. 9. Photomicrograph of colorless paragnaths on 
area I of a 17-segmented worm 17 days old. Dimensions 
top to bottom of area I, 70 g. 
noted; however, a statistical analysis of the 
offspring was not the subject of any special 
study. 
DISCUSSION 
A review of the literature on nereid devel- 
opment (summarized in Table 1, which gives 
the method of reproduction, the maximum 
stage to which the species has been reared, 
and the most recent reference) shows many 
different reproductive methods but apparently 
only two patterns of development. The most 
common method of reproduction is through 
epitoky. In this method the worms abandon 
their tubes or burrows at maturity and the 
sexual elements are emptied directly into the 
water, where fertilization and development 
ensue. These ova give rise to planktogenic 
larvae (Hemplemann, 1911). Both male and 
female die after spawning. This form of re- 
production has been observed and studied in 
Neanthes sue cine a, Nereis grubei, N. irrorata, N. 
pelagica, N. procera , N. vexillosa , Perinereis cul- 
trifera , P. marioni , Platynereis hicanaliculata , 
and P. dumerilii . Nereis vexillosa deviates 
slightly from the pattern in that the eggs are 
laid in a gelatinous egg mass, rather than 
singly. 
Swarming, without epitoky, followed by 
pairing and egg-laying, has been observed in 
TABLE 2 
Sequence of Events in the Life History 
of Neanthes caudata 
AGE IN 
DAYS 
CHARACTERISTICS 
7 
Elongation of egg; muscular movement; 
length 0.52 mm. 
8 
Appearance of three larval segments; anal 
cirri; hatching from egg capsule; length 
0.62 mm. 
9 
Four larval segments; tentacles; one pair of 
peristomial tentacles; length 1.0 mm. 
10 
Five larval segments; two pairs of peris- 
tomial tentacles; early palpi; jaws with 
terminal tooth only; length 1.1 mm. 
11 
Seven larval segments; three pairs of peris- 
tomial tentacles. 
13 
Animals with 12 adult segments; setae of 
first larval segment drop out, segment 
becomes peristomium; jaws with four 
lateral teeth; length 1.4 mm. 
14 
Animals with 14 segments; jaws with five 
lateral teeth; paragnaths on maxillary ring 
only. 
16 
Animals with 16 segments; jaws with six 
lateral teeth. 
21 
Animals with 18 segments; jaws with seven 
lateral teeth; jaws becoming dark brown 
at tips; paragnaths present on oral ring; 
worms have left parent tube and have 
built own mucoid tube; length 4.0 mm. 
23 
Animals with 24 segments; four pairs of 
peristomial tentacles; feeding; length 6.0 
mm. 
26 
Animals with 32 segments; paragnaths get- 
ting dark brown. 
33 
Animals with 42 segments. 
36 
Animals with 48 segments. 
40 
Animals with 51 segments. 
44 
Animals with 55 segments; eggs observed in 
coelom. 
65 
Female lays eggs with male incubating. 
92 
Male fertilized eggs from second female. 
148 
F 2 generation reproduced. 
203 
F 3 generation reproduced. 
Micronereis variegata , M. nanaimoensis , and 
Neanthes japonica . In the two species of Micro- 
nereis, the female lays the eggs in a gelatinous 
mass on the substrate and incubates them 
until the larvae emerge from the matrix. Fer- 
tilization takes place in the water mass in N. 
japonica. 
The female of Ceratonereis costae lays her 
eggs in a gelatinous matrix within her tube. 
Neither epitoky nor swarming precedes egg- 
