NO. 1573. 



PARASITIC COPEPODS— WILSON. 



337 



The transparent margin is also very irregular in pattern and \\adth, 

 especially opposite the bases of the locomotor appendages. 



The central mass of pigment reaches forward anteriorly in a long- 

 median, two-pronged projection and sends out branches also on 

 either side opposite the second pair of appendages and the balancers. 

 The anterior half of the body is more or 

 less transparent and shows the muscles 

 plainly, while the posterior part is 

 opaque from the presence of yolk gran- ^ \ / A 



ules (see fig. 4). 



Length, 0.25 mm.; width, 0,12 mm. 



THE METANAUPLIUS as seen in the 

 genus Nesippus. 



On molting fi-om the nauplius into 

 the metanauplius the body becomes 

 divided into regions consisting of a cara- 

 pace, two free thorax segments, and a 

 fusion of the genital segment and the 

 abdomen (fig. 6). The carapace has an 

 elongated acorn shape, the length twice 

 the width, and squarely truncated pos- 

 teriorly, with the corners produced into 

 narrow lobes reaching to the center of 

 the first free segment. The frontal plates 

 are large and prominent, but folded 

 under the anterior margin, so that very 

 little of them can be seen in dorsal view. 

 They are folded more evenly than in the 

 Alehion larva and do not leave conical 

 projections at the anterior corners. 

 The eyes are situated even farther back 

 than in Alehion, nearly half the distance 

 from the anterior margin. They are 

 quite large and not fused, although in contact on the mid-line. 



The first free segment is evidently a fusion of the second and third 

 thorax segments, as is indicated by the attachment of the legs. As 

 these two segments are more or less fused in all the adults belonging 

 to this subfamily, their fusion here in the matanauplius is what 

 would naturall}^ be expected. 



The fused segment is nearly as wdde as the carapace, and is fur- 

 nished with broad lateral lobes at the sides over the bases of the legs. 

 Such lateral lobes or plates are also characteristic of all the adults of 

 both sexes, but in later development they become longer and nar- 

 Proc. N. M. vol. xxxiii— 07 22 



-The metanauplius of 



sippus alatus. 



Ne- 



