Hawaiian Marine Gastropods — OSTERGAARD 
wall was very thin and transparent, so that 
the carmine-colored ova could be seen plainly 
without breaking the capsule. 
The ova, of which there were about 1,000 
in a case, averaged 0.15 mm. in diameter. 
Early in the afternoon of the same day they 
started to divide. Most of them reached the 
four-cell stage by 4:00 p.m. The mode of 
division was the same as that observed in the 
other species. 
Not until the seventeenth day did the lar- 
vae begin to leave the egg cases. Develop- 
ment had probably been retarded owing to 
unsuitable conditions, as many egg cases at 
that time contained dead embryos only. 
The veliger shell, which had attained a 
length of about 0.235 mm., differed from 
those of the other species which have here 
been described, particularly in its sculptur- 
ing. While a pitted condition of the surface 
might have been recognized, closely crowded, 
rounded granules gave to the shell a distinc- 
tive appearance. It had a slight golden tinge, 
a brown columella, and margin of aperture. 
Fig. 6. Cypraea mautniana Linnaeus, a-c, Shell 
of free-swimming veliger showing operculum 
lodged in shell; d, operculum in edge view; e, 
operculum showing spiral turns. 
85 
The operculum differed from those observed 
in the other species by being strongly convex 
on the surface that attached it to the foot 
(Fig. 6a-e). 
Cypraea poraria Linnaeus 
Fig. 7 
On May 1, 1923, an egg mass of Cypraea 
poraria that was attached to a coral rock from 
Honolulu harbor was brought to the labora- 
tory. The animal was "sitting” on the egg 
mass which, at the time it was obtained, was 
well along in development. 
free-swimming veliger with opercula and otocysts. 
A study was made of the veliger shell 
alone. This measured 0.14 mm. through its 
greater diameter, or length. It had a very 
delicately pitted surface of a pale golden- 
yellow coloration. The operculum, broadly 
rounded, was slightly concave longitudinally 
cn its free surface (Fig. la, b, c) . 
PROTECTION OF eggs by Cypraea Isabella 
LINNAEUS AND Cypraea helvola LINNAEUS 
As I was fortunate enough to obtain eggs 
from species of Cypraea kept in the labora- 
tory during the summer of 1921, it was possi- 
ble to observe the strong maternal instinct 
developed in these mollusks as shown by the 
protection of their eggs. 
Cypraea Isabella deposited its egg mass on 
the side of the glass in which it was kept, a 
few days following its capture. The egg mass, 
consisting of about 1,500 cases imbedded in 
a ge’atinous matrix, was spread out so as to 
be conveniently covered by the foot of the 
animal. Various interesting methods em- 
