MUSEUM OF COMPARATIVE ZOOLOGY. 309 
Plate I. Fig. 8, represents an embryo further advanced. The abdo- 
men has lengthened to such an extent that it entirely conceals the 
labrum, and extends forward so as to almost meet the tip of the rostrum 
(rs), which lies bent beneath the head. The maxillipeds have increased 
in length, and extend forward as two-branched appendages on each side 
of the abdomen. At the base of the rostrum is the simple median eye 
(oci); the permanent eyes (oc) show through the egg-shell as oval 
black spots. 
In the still older embryo in the egg represented on Plate I. Fig. 9, 
the unabsorbed yelk (vt) has so diminished as to appear as a large 
greenish patch on the dorsal side of the embryo. The whole margin of 
the carapace is clearly defined, and its posterior or cardiac portion is 
unobscured by underlying yelk. The eyes (o c) now form two black round- 
ish spots at the anterior end of the embryo, so large that they are very 
conspicuous to the naked eye. The corneæ and cones are now formed, 
and the eye is thrust out a little upon a very short stalk. The antenna 
of the first pair (Z) are divided into two segments, a long.proximal and 
a short oval distal one. The latter is furnished with a few sete at its tip. 
The two branches of the second antenne (77) are also tipped with setae. 
In the eourse of the development of the embryo within the egg, 
the egg has become larger than it was when first laid. A few hours be- 
fore hatching (Pl. Į. Fig. 10), it measures 1 mm. in long diameter, A 
small patch of yellowish green (vit) just behind the eyes is the only 
remnant of the unabsorbed yelk. The abdomen (a b) has lengthened to 
such an extent that it reaches far beyond the mouth, between the eyes, 
to the dorsal side of the head. The basal segment and the two branches 
of the second pair of antenne are now clearly defined, and have acquired 
very nearly the form which they have in the larva after hatching. The 
maxillipeds have grown to a very large size, and conceal the oral ap- 
pendages in front of them. 
Embryos removed from the egg an hour before hatching (Pl. I. 
Fig. 11) disclosed two pairs of two-branched sac-like appendages (Figs. 
11, 13, ZX, X), concealed between the bases of the third maxillipeds. 
These are the rudiments of the two pairs of chelipeds of the adult 
prawn. The structure of the embryo is now the same as during the 
first larval stage. 
First Larval Stage (Pl. I. Figs. 14 — 18 ; Pl. II. Fig. 1). — When it 
first issues from the egg the young prawn is 24 mm. in length. The 
carapace is broad, produced between the eyes into a long, pointed ros- 
trum. At the base of the rostrum is a small simple eye. The com- 
