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PACIFIC SCIENCE, Vol. XV, April 1961 
exit window 
ndth 
stalk 
basal plate 
1 
Fig. 1. Generalized egg capsule of Conus, with 
terms used in presentation of dimensions. 
tritive, material are passed out of the genital 
aperture of the female downward through a tem- 
porary groove on the side of the foot to the 
egg capsule gland, which is situated on the an- 
terior portion of the sole. The fluid mass of 
eggs passes into the aperture of the gland, in 
which horny egg capsules are produced. This 
method of egg capsule formation is character- 
istic of the Neogastropoda, in contrast to the 
Mesogastropoda in which the capsule is secreted 
in the genital ducts and only moulded and 
hardened by the egg capsule gland (Ankel, 
1929; Fretter, 1941). 
The general shape of the capsules (see Fig. 
1) is "like a flattened pouch or flask” (Knud- 
sen, 1950). As will be shown below and in a 
forthcoming paper (Kohn, ms), there is a 
moderate degree of interspecific variation in the 
form of the egg capsules and, in some species, 
considerable intraspecific variation. It is usually 
not possible to determine the species to which 
an egg mass belongs in the absence of the 
parent. This is in marked contrast to the egg 
capsules of some other prosobranch genera, e.g., 
Mur ex and Nassa, which are highly species- 
specific (Thorson, 1959). 
The capsule is typically white or straw-col- 
ored and is presumably constructed of conchy o- 
lin, a scleroprotein. The capsules are deposited 
in clusters which frequently consist of several 
short rows of a few capsules each. A cluster of 
egg capsules is referred to as an egg mass, fol- 
lowing Thorson ( 1940, et seq .) and others. The 
number of capsules deposited in a cluster and 
the number of eggs per capsule are variable. 
In the material collected in Hawaii, the number 
of capsules per cluster ranged from 1 to 68 
( Table 1 ) and the number of eggs per capsule 
from 80 to about 10,000 (Table 2). 
In most species, each capsule is attached to 
the substratum, usually the underside of a rock, 
by an adhesive basal plate (Fig. 1). There is 
a narrow, short stalk, above which is the cap- 
sule proper. Its walls are thin, nonrigid, and 
translucent, and they usually bear ridges on the 
flat surfaces. The lateral edges are typically con- 
vex, and there is a preformed exit window along 
the straight, uppermost part of the capsule. It 
is covered by a hyaline membrane or operculum, 
which is never very thick and appears to be- 
come thinner and more transparent as develop- 
ment proceeds. The hatching process has not 
been studied closely, but it appears that the 
entire membrane dissolves prior to escape of 
the larvae. This is in contrast to the family 
Muricidae, in which the egg capsule is closed 
by a thick operculum which is lost intact at 
hatching (Ankel, 1937; Hancock, 1956). Dis- 
solution of the operculum may be due to an 
enzyme liberated by the larvae just prior to 
hatching (Ankel, 1937). The larvae of Conus 
do not occupy the entire capsule before hatch- 
ing. 
DEVELOPMENT WITHIN EGG CAPSULE 
To study the course of larval development, 
egg masses were kept in constantly aerated 
running sea water in finger bowls or wide- 
mouth 4-1. jars. Following hatching, the larvae 
were kept in the larger jars in aerated, but not 
circulating, sea water. In some cases, sand and 
coral rocks from the normal habitat were placed 
on the bottom of the vessel in an effort to in- 
duce settling of the larvae, but this was gen- 
erally unsuccessful. Details of embryonic de- 
velopment are described below for those species 
in which they could be determined, and present 
knowledge of development in Conus is re- 
viewed in the section, Discussion. 
Conus abbreviatus Reeve 
A cluster of 33 egg capsules was found at- 
tached to the underside of a metal refuse can 
