Hawaiian Marine Gastropods — OSTERGAARD 
107 
Family PLEUROBRANCHIDAE 
Genus Pleurobranchus 
Pleurobranchus sp. 
Fig. 33 
On July 25, 1922, a small species of Pleu- 
robranchus was found on the windward side 
of Moku O Loe, Kaneohe Bay, and brought 
to the laboratory. An egg filament, which 
for the size of the animal seemed very large, 
was laid by this mollusk. It was about 18 cm. 
in length with a diameter of about 4 mm. 
It was white and transparent and contained 
what appeared to be a continuous thick- 
walled tube wound circularly with the fila- 
ments in close contact with one another. A 
single layer of ova, each ovum measuring 
about 0.08 mm. in diameter and enclosed by 
a spherical capsule, lay closely packed within 
this inner tube (Fig. 33 a, b ). 
The embryos attained their free-swimming 
larval stage in 6 days, at which time they 
had a pair of large, rounded, colorless veliger 
lobes with conspicuous eye spots, a pointed 
foot without a visible operculum, otocysts, 
and a large black pigment spot located near 
the left side. The viscera were pale greenish- 
yellow. The shell, which measured 0.125 mm. 
in length, was clear and colorless (Fig. 
33 c-g). 
Suborder ascoglossa 
Family PLACO BRAN CHID AE 
Genus Placobranchus 
Placobranchus sp. 
Fig. 34 
A large number of Placobranchus sp. was 
brought in from Molokai in late February, 
1923, and kept in the living state in the lab- 
oratory for several months. None of these 
laid eggs. But a specimen found near the 
Elk’s Club, Waikiki, during March, 1923, 
deposited a white cylindrical filament, about 
19 mm. in length and nearly 1.5 mm. in 
Fig. 33- Pleurobranchus sp. a, Egg filament; 
b, magnified section of filament showing circularly 
arranged tubes containing ova; c, d, free-swimming 
veligers; e-g, shells of free-swimming veligers. 
diameter, which tapered to a point at each 
end. At the middle of the filament, the ova 
lay 9 or 10 abreast in cross section; each 
was enclosed in a globular capsule of about 
0.16 mm. in diameter (Fig. 34^, b). 
