68 
PACIFIC SCIENCE, Vol. XV, January 1961 
Fig. 1. Sagitta bierii. a, Ventral view; b, dorsal view; 
c, hook; d, left eye. 
of the body resembles Sagitta decipiens Fowler. 
That species, however, is more transparent and 
flaccid and differs in the position of the fins 
and in having hooks without serrations. 
The anterior fins begin at the level of the 
posterior end of the ventral ganglion. They 
broaden at their posterior end and are without 
a rayless zone. 
The posterior fins begin at a short distance 
from the posterior end of the anterior fins and 
end at the level of the seminal vesicles. They 
are somewhat roundly triangular in shape and 
about the same or slightly longer than the an- 
terior fins. They are broadest behind the tail 
septum, but their greatest length lies in the 
trunk region. They do not have a rayless zone 
(Fig. la). 
The head is small, slightly elongated in the 
longitudinal axis, and thus differs from 5*. decip- 
iens Fowler, which has a larger head (Fig. lb). 
The hooks have strong serrations as in other 
species of the " serratodentata group.” The ser- 
rations are very conspicuous with low magni- 
fications (Fig. 1 c). 
The eye pigment forms a kidney-shaped body 
which in the long axis is one-half the width 
of the eye, with the longitudinal diameter longer 
than the transverse (Fig. Id ) . 
The collarette is small. 
The seminal vesicles are triangular to pear 
shape and not very conspicuous. The species is 
not as protandric as most chaetognaths (Figs. 
2a, b, 3 a). In about 60,000 specimens studied, 
less than a dozen appeared with the seminal 
vesicles well developed or undamaged. The sem- 
inal vesicles do not touch the tail fin. 
The ovaries are long, fine tubes; when mature 
they reach to the posterior end or the middle 
of the anterior fins. The right ovary is usually 
shorter. Viewed laterally, the alternated posi- 
tion of the ovulae is clearly seen (Fig. 3 b) . 
The number of ovulae in mature specimens 
is from 30 to 48. 
LENGTH: In a well-mixed population the 
most abundant size is 12-14 mm. In April, 
1958, from Monterey northwards, the prevailing 
size was from 14 mm. to 17 mm. The northern 
specimens all had stronger bodies and those 
from 13 to 15 mm. in length were mostly im- 
mature (Fig. 4). 
