78 
PACIFIC SCIENCE, Vol. IV, April, 1950 
Egg structure not capsular ... 24 
24 (23) Egg structure a gelatinous mass 
25 
Egg structure not a gelatinous 
mass but orbicular or fan- 
shaped and of great size. Di- 
ameter 15 cm., thickness 
about 2 mm. Ova grouped 
together in masses of about 
50, visible to the unaided eye 
and arranged in transverse 
rows of about 50. Color pale 
yellow. . . Tonna perdix, p. 96 . 
25 (24) Egg mass consisting of a glob- 
ular, soft, clear gelatinous 
matrix about 18 mm. in di- 
ameter in which about a thou- 
sand purple-colored ova are 
imbedded 
.... Atys semistriata, p. 105. 
Egg mass of irregular outline, 
tough, gelatinous, and pasted 
flatly to any surface, occupy- 
ing about 5 square cm. Color 
lemon yellow 
Peronia sp., p. 112. 
Order PROSOBRANCHIATA 
Family CYPRAEIDAE 
Genus Cypraea 
Cypraea carneola Linnaeus 
Figs. 1, 2 
On June 8, 1921, a large adult specimen 
of Cypraea carneola was found on the Wai- 
kiki reef, off the Marine Biological Labora- 
tory of the University of Hawaii. This species 
is not of common occurrence in wading 
depths on the Hawaiian reefs. 
The specimen was brought to the labora- 
tory and placed in a trough with running 
water, and the following night it deposited 
an egg mass on the enameled surface of a 
pan in which it was placed. The egg mass 
consisted of about 1,000 egg capsules which 
were imbedded in a firm gelatinous substance. 
The individual egg capsule, or egg case, is 
about 4 mm. long and is triangular, with its 
flattened base attached to the substratum or 
to another egg capsule. From its base the 
egg capsule curves slightly to a somewhat 
obtuse point (Fig. la). Its firm parchment- 
like walls are pale yellow and contain, in a 
clear viscid capsular fluid, an average of 500 
ova (Fig. lb). 
During the first day the animal remained 
constantly on its eggs, covering the entire 
mass with its foot; thereafter, probably due 
to having been removed several times, it left 
its "nest” voluntarily and stayed away. 
Under the compound microscope the clea- 
vage of the zygote was studied, as were the 
resulting embryos as far as the free-swimming 
larval stage. 
The ovum is about 0.14 mm. in diameter, 
and a concentration of cytoplasm containing 
the nucleus appears as a clear area about one- 
fifth the diameter of the ovum. This in turn 
is surrounded by a dark area, while somewhat 
globular yolk granules constitute the bulk oi 
the ovum (Fig. 1 c) . 
Upon examination of the contents of one 
of the egg cases the morning after they were 
laid, none of the zygotes was found to have 
started cleavage. The contents of another egg 
case, however, opened at 4:00 P.M. of the 
same day, revealed many in the two-cell stage 
scattered among those which had not started 
cleavage. 
This is a telolecithal egg with holoblastic, 
or total, cleavage, the first two divisions being 
equal, the third unequal. The first cleavage 
is vertical and passes through the animal and 
vegetal poles of the zygote, dividing it into 
two blastomeres of equal size. The animal, 
or formative, pole is clearly discernible by 
the position of the nuclei, the nucleus of each 
daughter cell being directly opposite that of 
the other, and close to the cleavage plane 
(Fig. Id). 
An hour later, at about 5 : 00 P.M., the sec- 
ond division began to take place; and in the 
