N1COTHOE. 305 



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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