N1C0TH0E. 
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ova into the larva state. In such creatures it is extremely 
difficult to trace their full development up to maturity ; 
but Rathke has observed that the young of the Nicothoe 
are considerably advanced in development before they 
leave the ovary, and that while there, some of these em- 
bryos attain a considerably larger size than others, and 
pursue a somewhat different progress. The one, the 
larger kind, Rathke considers may be the female, and the 
smaller the male, though he confesses that the smaller 
form is the most abundant in the ovaries. The larger 
embryo has a flat appearance, and consists of a very large 
and broad upper portion or cephalo-thorax, and a narrow 
posterior portion, nearly of the same length as the upper. 
The upper part, or cephalo-thorax, is rounded and nar- 
rower in front, much expanded laterally, and contracts 
again posteriorly. On the upper part of the dorsal sur- 
face, situated near the edges, we see two light, reddish- 
brown points, one on each side, which are no doubt the 
eyes ; while it is equally clear, the large lateral expansions 
become the wing-shaped appendages in the adult. 
On the ventral surface we see, at the upper part, two 
antennae of considerable size, consisting of three stout 
articulations ; and a little below these organs we see a pair 
of short members, of one joint, forming pretty strong 
hooks or curved claws, which are no doubt the first pair 
of foot-jaws. Between these organs we find, exactly in 
the centre, a small protuberance, representing the organs 
of the mouth ; and at some distance below this we see two 
other pairs of members, the first of which consists of two 
joints, the basal, stout and of considerable size, the ter- 
minal much smaller, and ending in a strong hook-shaped 
claw. The second pair is much larger, and is formed of 
three articulations, the middle one the longest, and the 
terminal armed at the extremity with a stout claw. These 
two pairs of organs are the second and third pairs of foot- 
jaws in the adult. A little lower still, close to the posterior 
margin of the cephalo-thorax, we see another pair of mem- 
bers, flat and of considerable length. They consist of 
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