592 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



Fig. 11.— Egg filament and developing 



EGG OF CLAVELLISA CORDATA. 



appear. But here in the Lernaeopodidae the mouth parts and the 

 first two pairs of swimming legs appear simultaneously with the 

 nauplius appendages, and they all develop together. The early larval 

 stages are thus so thoroughly fused as to become virtually one single 

 period, and the pecuharities which characterize the different stages 



overlap one another, several some- 

 times being present at the.same time. 

 Understanding such a fusion, there- 

 fore, we may distinguish the follo\ving 

 steps in development by dissecting 

 some of the larvae out of their sur- 

 rounding envelopes. 



Nauplius. — Body ovate, the larger 

 end anterior; two pairs of appendages 

 visible, corresponding to the first 

 and second antennae; first pair one- 

 jointed, uniramose, terminating in 

 two plumose setae; second pair biramose, exopod five-jointed, each 

 joint with a long plumose seta, endopod two-jointed and termi- 

 nated by two plumose setae; no balancers but the posterior portion 

 of the body differentiated into a free thorax and a broad spatulate 

 abdomen, which is curled over ventrally beneath the thorax; no 

 eye visible but the anterior part of the head occupied by an attach- 

 ment filament which forms a simple loop, extending from 

 the frontal margin to the center of the head; behind this 

 may be seen the yolk granules and on either side are the 

 muscles that later will move the swimming legs. 



Metanawplius . — Body so thick and stout as to be nearly 

 spherical; first antennae three-jointed and tipped with 

 two plumose setae; second pair with a five-jointed exopod, 

 each joint with a plumose seta, and a two-jointed endopod, 

 mth two terminal setae and a stout claw at their base; 

 upper Hp eUiptical, wider than long; mandible short, 

 uniramose, and tipped with a single seta; first maxillae 

 biramose at the tip, the outer ramus much shorter than 

 the inner, and each armed with short spines; second 

 maxillae stout, uniramose, three-jointed and terminated by a weak 

 claw; maxilhpeds also uniramose and three-jointed and terminated 

 by a stouter claw. 



Each of the four swimming legs consists of a basal joint and two 

 one-jointed rami, armed with long ])lumose setae; the anal laminae 

 are as large as the rami of the legs and carry long and unequal setae. 

 The fii'st actual molt takes place at the close of this metanaupfius 

 stage, and the escape from the egg is simultaneous with it. 



Fig. 12.— Egg 



filament 

 and egg of 

 Naobran- 

 chia lizae. 

 Figs. 10, 11, 



AND 12 ARE 

 MAG NITIED 

 ALIKE. 



