i 10 
PACIFIC SCIENCE, VoL IV, April, 1950 
flat ribbon of two volutions, about 14 cm. in 
length and 6 mm. in width. The structure 
was closely packed with oval and triangular 
egg cases containing from one to three ova 
each. The ova were about 0.06 mm. in diam- 
eter (Fig. 38 a, b). 
The free-swimming stage was attained in 
9 days, when a pale brownish larva emerged. 
On the right side of the body of the larva 
was an irregular black pigment spot and near 
it another of dark orange. Otocysts were 
present, but not eyes. A broad operculum 
and a clear and pellucid shell were present 
(Fig. 38c, d). 
Family AEOLIDIIDAE 
Genus Aeolidia 
Aeolidia sp. 
Fig. 39 
During the month of April, 1922, a num- 
ber of egg structures were deposited on a rock 
in the laboratory by a species of Aeolidia . 
They were flat, bright yellow ribbons about 
18 mm. long and 2 mm. wide, of one volu- 
tions which was so close that the inner mar- 
gins, by which the mass was attached, almost 
touched (Fig. 39^ b). The ova were strung 
out in single rows within transverse gelat- 
inous tubes which radiated from the inner 
margin of the ribbon. A row contained an 
average of 15 ova. The spaces between the 
transverse tubes toward the outer margin also 
contained ova (Fig. 3 9c). The ova, which 
measured about 0.17 mm. in diameter, were 
contained singly in oval capsules. 
This is the most prolific mollusk in point 
of numbers of egg structures yet observed. 
Nine ribbons were deposited by the same 
animal within 12 days, one each day for sev- 
eral days. Two more mollusks of this species 
were brought in from near the Elk’s Club, 
Waikiki. Both animals were on a living coral 
head, Pontes compressa, to which were at- 
tached half a dozen or more egg ribbons. 
During 10 days of captivity the number of 
ribbons deposited by them had increased to 
30. The ribbons were all of a very pale yel- 
low and nearly all of them were larger than 
those of the first lot, most of them being 
twice as great in diameter. 
The eggs of all the ribbons seemed to 
develop and the free-swimming stage was 
reached in 6 days. The eyespots in this larva 
were large and prominent, as were foot and 
Fig. 39. Aeolidia sp. a , Egg ribbon; b, ribbon 
enlarged; c, magnified section of ribbon showing 
arrangement of ova; d, egg ribbon laid by another 
individual; e, f, free-swimming veliger larva: e, 
ventral, and f, lateral aspects. 
operculum. The viscera had a marked yel- 
lowish tinge, but the foot and velum were 
almost colorless. The shell, measuring 0.225 
mm. in length, is pellucid and colorless (Fig. 
39 e, /). 
