101 
embryo in the form of a double series of bud-like prominences. Of these, however, 
the 3 anterior pairs are somewhat in advance of the others in development, being 
rather distinctly defined, while the other 9 pairs can be but faintly traced (see 
fig. 4). These 3 anterior pairs of limbs represent the 2 pairs of antennae and 
the mandibles, which, as is well known, are also those first appearing in other 
Crustacea, characterising the so-called Nauplian stage. The 1st pair (a 1 ), repre¬ 
senting the superior antennae, are much larger than the other 2, and have the 
form of 2 spatulate plates, slightly bilobular at the tip, and extending backwards 
on the sides of the embryo. The 2 succeeding pairs (inferior antennce and 
mandibles, a 3 , M) also extend somewhat laterally, and are simple conic in form. 
Between them in the middle, the ventral face projects as a rounded prominence 
(L), representing the anterior lip or labrum. The remaining 9 pairs of limbs, as 
stated above, are at first but very faintly defined and of rather uniform appear¬ 
ance, causing a slight crenulation of the ventral face. 
In a succeeding stage (fig. 5) the egg-membrane or chorion is cast off, 
and the 3 anterior pairs of limbs thereby become freely projecting, whereas the 
others are still enveloped by the thin larval skin. The dorsal cleft has deepened 
considerably, and extends somewhat obliquely behind, whereby the anterior 
broadly rounded e'xtremity is defined clearly from the somewhat narrower 
posterior extremity. The latter has given origin on each side to a knoblike 
prominence (urp), indicating the developing uropoda. The 3 antex-ior pah's of 
limbs have not greatly changed their appearance. The remaining pairs, on the 
other hand, now appear vei’y distinctly, and the 2 anterior of these (m 1 , m 2 ), 
representing the 2 pairs of maxillae, distinguish themselves from the succeeding 
7 pairs both by their form and more lateral position. They are also placed 
somewhat more apart, though the anterior pair partly cover the postei'ior. The 
former has developed a small lateral ramus (the reflexed palp), and the latter 
appears slightly trilobate at the end. The 7 succeeding pairs of limbs have 
a vei'y similar appearance, each terminating in a conical, posteriorly-curving 
process (the endopodite), and having outside a knob-like protuberance (the 
exopodite), which, however, in the 2nd and 2 last pairs is almost obsolete. In 
the 3 middle pairs, representing the 3rd pair of maxillipeds (mp 3 ) and the 2 
first pairs of legs (p l , p 2 ) this protuberance is easily obsei’vable; and in the 
1 st pair (mp 1 ), representing the 1st pair of maxillipeds, an evidently homologous 
outer appendage is also seen; but it here issues somewhat higher up than in the 
other pairs, and subsequently also becomes different in form and direction. It 
represents the exopodal part of the branchial apparatus, the epipodal part being 
apparently not yet formed. Just above the maxillae, there is seen on each side of 
14 — Crustacea. 
