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PACIFIC SCIENCE, Vol. IV, April, 1950 
number of ova contained in the whole struc- 
ture gave the figure of 10,206,000 (Fig. 
3 2b). 
When examined in the morning of the 
day on which they were found the ova 
showed no signs of segmentation, but in the 
afternoon two- and four-cell stages were seen 
in many capsules, although many of the ova 
were still unsegmented. Adjoining capsules 
showed different stages of development, but 
the embryos in each capsule were usually 
of the same stage. The ovum was about 
0.08 mm. in diameter and the first and second 
divisions resulted in blastomeres of nearly 
equal sizes (Fig. 3 2c, d, e ) . Succeeding stages 
of cleavage were not observed, but after the 
third day of incubation when the embryos 
had developed minute cilia, movement could 
be noticed. At the fourth day they showed 
high activity and the shell was apparently in 
the process of formation. A large, very con- 
spicuous brown spot had now developed, 
usually on the right side of the body. After 
the sixth day of incubation the veliger lobes 
grew out and the shell covered the body. 
Neither eyes nor otocysts could be distin- 
guished at this stage. 
On the tenth day of incubation a large 
number of embryos launched upon their free- 
swimming larval existence. Otocysts, but no 
eyes, were present, as was a large operculum 
projecting beyond the tip of the foot and 
curving upward laterally. The shell was 
plain, colorless, and translucent (Fig. 32/, g). 
0. 1 mm. 
Fig. 32. Umbraculum sinicum (Gmelin). a, Egg ribbon; b, magnified section showing hyaline 
capsules with ova; c—e, cleavage stages; f, early veliger; g, free-swimming veliger larva. 
