Hawaiian Marine Gastropods — OsTERGAARD 
Family SCAPHANDRIDAE 
Genus Atys 
Atys semistriatus Pease 
Fig. 31 
On August 22, 1921, an egg mass was 
laid in the laboratory by a specimen of Atys 
semistriatus which had been found near-by. 
The egg structure consisted of a globular 
mass of a soft, clear, gelatinous matrix, about 
18 mm. in diameter, in which a thousand or 
more purple ova were imbedded in a spher- 
ical mass and surrounded by a thin layer of 
the matrix. Each ovum was enclosed in an 
oval hyaline capsule whose greatest diameter 
b, ova within hyaline capsules, magnified; c, d, 
veliger stage before hatching; e, f, shell of veliger 
larva with operculum. 
105 
was about 0.2 mm.; the ovum measured 
about 0.09 mm. (Fig. 31*. b) . 
Segmentation seemed very rapid, for the 
eggs, laid in the morning, were found to have 
attained a many-celled stage in the afternoon. 
Three macromeres were present at the veg- 
etal pole, and the animal pole was capped 
with micromeres. About 24 hours later the 
embryos had become whirling ciliated gas- 
trulas or trochophores. 
The embryos did not reach their free- 
swimming stage, all dying within the matrix, 
but they reached an advanced veliger stage 
after 4 days’ incubation. The velum was large 
with long cilia, the foot rather short and 
broad with a broad, triangular operculum. A 
rather ample, colorless, and transparent shell 
enclosed the visceral portion of the larva. A 
large purplish-red digestive gland could be 
seen in the region of the stomach, near 
which a well-defined intestine ran out to the 
anus beyond the margin of the shell. The 
eyes consisted of small pigment specks. Oto- 
cysts were not seen (Fig. 31 c—f). 
Family UMBRACUL1DAE 
Genus Umbraculum 
Umbraculum sinicum (Gmelin) 
Fig. 32 
A specimen of Umbraculum sinicum, found 
near Waialua, Oahu, was brought to the lab- 
oratory. On the morning of June 25, 1921, 
a pink, garland-like egg structure was seen 
projecting from under its foot. 
This structure consisted of a thin ribbon, 
15 mm. in width, intensely folded upon itself 
and attached to the rock by one edge. It was 
wound three and one-half times around and 
measured about 12 cm. in diameter (Fig. 
32*). 
The ribbon was closely packed with glob- 
ular capsules forming one or two layers. 
These capsules were quite uniform in size, 
0.5 mm. in diameter, and each contained 
about 30 ova. A conservative estimate of the 
