Hawaiian Marine Gastropods — OSTERGAARD 
103 
attached to alga and later identified as that 
of Hydatina pbysis was found near the aquar- 
ium tank. It was about 25 mm. in length, 
half as wide, and intensely folded, much like 
that of H. amp lustre . A single layer of hy- 
aline capsules, each containing five or six em- 
bryos, lay between the walls of the structure 
(Fig. 27a, b). 
Fig. 27. Hydatina physis (Linnaeus), a, Egg 
structure; b, egg envelopes with veligers magni- 
fied; c, d, free-swimming veliger larva: c, lateral, 
and d, ventral aspects. 
When the structure was obtained the em- 
bryos were far along in development. The 
veliger larva had a faint greenish tinge, and 
was a little smaller than that of H. amplustre. 
Gtocysts and a prominent operculum were 
present. The shell, measuring 0.11 mm. in 
length, was colorless, like that of the preced- 
ing species. The muscle attaching the larva 
to the shell was clearly seen (Fig. 21c, d). 
Family ACTAEONIDAE 
Genus Bullina 
Bullina scabra solida Pilsbry 
Fig. 28 
A specimen of Bullina scabra solida found 
at Kahala reef was placed in a dish of water 
in the laboratory. Two days later, on the 
morning of March 23, 1921, the mollusk had 
deposited an egg filament in the dish. 
The filament was a short, white, cylindri- 
cal tube, arranged in a spiral with one end 
attached to the bottom of the dish by means 
of a gelatinous material. The eggs were of 
varying sizes, quite numerous, and had no 
orderly arrangement within the structure, 
each being enclosed within a capsule. The 
animal was pure white and resembled closely 
Hydatina amplustre (Linnaeus) (Fig. 28^, b, 
c). Development was not observed. 
Fig. 28. Bullina scabra solida Pilsbry. a, Ani- 
mal that laid the egg mass; b, egg filament; c, sec- 
tion of coil magnified. 
Family BULLIDAE 
Genus Bulla 
Bulla sp. 
Fig. 29 
On November 22, 1922, two specimens of 
Bulla were brought to the laboratory from 
the adjacent water. An egg filament was laid 
by each mollusk the same day. These were 
comparatively thick cylindrical filaments, 3 
cm. in length and 1 mm. in diameter. Each 
