500 PROCEEDINGS OF SCIENTIFIC SOCIETIES. 
ing amount of sea water, in which the embryo revolves. At a little later 
period the embryo throws off an embryonal skin, the thin pellicle floating 
about in the egg. 
Still later in the life of the embryo the claws are developed, an addi- 
tional rudimentary gill appears, and the abdomen grows broader and lar- 
becomes broad an at, the abdomen being a little more than half as 
es 
oO 
3 
B 
© 
ct 
ü 
o 
mS 
ct 
zm 
© 
e 
e 
"3 
BE 
£e 
— 
o 
c 
zz 
o 
5 
= 
nu 
2g 
5 
4 
m» 
EB 
e 
t 
n 
$ 
e 
e 
a 
p: 
un 
=, 
=] 
q 
f 
p! 
vn 
a 
4°) 
£g 
e 
| 
ct 
whole embryo bears a very near resemblance to certain genera of Tri- 
lobites, as Trinucleus, Asaphus and others. 
ut six weeks from the time the eggs are laid the embryo hatches. 
It differs chiefly from the previous stage in the abdomen being much lar- 
ger, scarcely less in size than the cephalothorax; in the obliteration of 
scarcely projecting beyond the edge of the abdomen. It forms the ninth 
segment. The young swim briskly up and down the jar, skimming about 
on their backs, by flapping their gills, not bending their bodies. 
Conclusions. The eggs are laid in great numbers loose in the sand, the 
male fertilizing them after they are dropped. This is an exception to the 
ularly laminated chorion, there is an inner egg membrane composed of 
rudely hexagonal cells; this membrane increases in size with the growth 
of the embryo, the chorion splitting and being thrown off during the 
