308 BULLETIN OF THE 
The appendages back of the mandibles now appear in regular suc- 
cession in the form of hyaline protuberances from the opaque yelk. 
Four days after the gastrula-stage (Pl. I. Fig. 3), the embryo has the 
form portrayed on Plate I. Fig. 4. 
The rudiments of the appendages have appeared as far back as the 
sixth pair (first pair of maxillipeds). The second pair of antenne (Pl. 
1 Fig. 4, 17), are now double appendages, the two parts representing 
the flagellum and scale of the future antenna. "The appendages behind 
the mandibles are bilobed from the time of their earliest appearance. 
The labrum (/5) has moved backward, so as now to lie on a line with 
the second pair of antenne. 
The antenne rapidly increase in length, assuming the form of ribands 
which lie along the outer side of the following appendages, parallel with 
the abdomen. Three days after the stage last described they reach as 
far back as the first pair of maxillipeds (Pl. I. Fig. 5), The first pair 
(1) lie on the outer side of the second pair (77), and are slightly shorter 
than these. The outer branch of the second pair, again, is a little 
longer than the inner branch. Even at this early period traces of setze 
are seen on the extremities of both pairs of. antenne. The rudiments 
of the appendages are now formed as far back as the third pair of max- 
illipeds (Pl. I. Fig. 5, VIII), the abdomen (ab) extends forward so far 
as to meet the labrum (15), but is still unformed along the median dorsal 
line. Some scattered blotches of a dark color (oc) are the first indica- 
tions of the pigment of the compound eye.* 
On the following day (Aug. 5) I observed the first appearance of the 
median simple eye in the form of a black pigment-spot in the middle 
line of the head. 
The embryo gradually encroaches upon the unabsorbed yelk-mass on 
the dorsal side of the egg. The outline of the carapace (Pl. I. Fig. 6, 
cp, four days before hatching) comes into view, extending posteriorly 
beyond the third pair of maxillipeds. Under the posterior part of the 
carapace the heart appears as a transparent pulsating sac (At). The 
abdomen (a6) becomes divided into segments by transverse constrictions 
which begin on the ventral side, the side which is applied to the ventral 
face of the cephalo-thorax of the embryo. Within the abdomen are 
seen the ganglia of the nervous system (Pl. 1. Fig. 6, ng). The end of 
the abdomen is produced into two blunt lobes, on the borders of which 
the sete are already visible. 
* The development of the eye certainly lends no countenance to the view that its 
stalk is an appendage homologous with the antenne, ۰ 
