Hawaiian Marine Gastropods- — OsTERGAARD 
83 
Some of the larvae which survived until 
the ninth day of their free-swimming stage 
gave no evidence of metamorphosis. 
Cypraea helvola Linnaeus- 
Fig. 4 
On July 23, 1921, 1 obtained from a porous 
rock in shallow water off the laboratory two 
adult specimens of Cypraea helvola , one of 
which was "sitting” on an egg mass deposited 
on the rock. 
The egg cases, or capsules, numbering 
about 1,000, were in many layers, imbedded 
in a gelatinous matrix with their long axes 
directed radially. The egg mass measured 
about 13 x 18 mm. (Fig. 4a). 
The egg case was somewhat oval, about 
2 mm. in length, of a pale straw color like 
those of C. carneola and C. Isabella, and con- 
tained about 200 ova. The capsule walls were 
thinner than those of the other two and quite 
transparent. 
Figure 4b shows a magnified capsule with 
embryos in the veliger stage. 
When the egg capsules were obtained, they 
were found to contain embryos in the gas- 
trula stage and were several days along in 
their development. The gastrulae were quite 
spherical and had been produced by epiboly, 
no sign of invagination being perceptible. 
The transverse measurement of the embryo 
in this stage was about 0.09 mm. (Fig. 4c). 
A little later the gastrula became slightly 
elongate and a small tuft of minute cilia ap- 
peared on each side of the body anteriorly, 
as in the two preceding species (Fig. 4d) . 
In the course of 3 days these embryos be- 
came free-swimming veliger larvae, which 
bore a close resemblance to those of C. car- 
neola of the same stage, except for being 
much smaller. As in that species, there was 
a large purple area on the ventral side of the 
foot (Fig. 4e, f). 
Some of the larvae were kept in jars with 
standing water for about a week of their 
free-swimming stage without showing any 
perceptible change. Upon hatching they is- 
sued from the egg cases simultaneously. The 
cases were purple, owing to the pigment in the 
larvae and the transparency of their covers. 
Fig. 4. Cypraea helvola Linnaeus, a, Egg mass; 
b, egg capsule enlarged with embryos in veliger 
stage; c, d, gastrula stage; e, f, free-swimming veli- 
ger stage: e, ventral, and f, lateral aspects; g—i, 
shell of free-swimming veliger showing operculum 
and otocysts. 
The veliger shell measured 0.14 mm. in 
length, and in a number of specimens trom 
which the dead animals had been removed 
by protozoan scavengers, opercula and oto- 
cysts remained. The pitted surface of the 
shell resembled that of the two preceding 
species- (Fig. 4 g, h, i): ' I 
Cypraea caputserpentis Linnaeus 
Fig. 5 
The commonest species of the genus in 
Hawaii is Cypraea caputserpentis. It is com 
